Is there a rule concerning the offloading of a missing passenger's baggage? Is there an International Rule under which the baggage of a passenger is offloaded in the case that he/she fails to report at the departure gate 15 minutes before boarding time?

This question was covered over on travel.stackexchange and seems like there is a European reg on it.

  In Europe, the question is covered by Regulation EC 300/2008. Annex I,
  section 5.3 reads

  Baggage reconciliation

    Each item of hold baggage shall be identified as accompanied or
    unaccompanied. Unaccompanied hold baggage shall not be transported,
    unless that baggage has been either separated due to factors beyond
    the passenger’s control or subjected to appropriate security controls.

I cant find any hard regulations but there seems to be some discussions floating around that would imply a domestic US flight may depart with your bags and without you here in the states.

I can speak from experience while on a flight departing CDG for DUB the plane was held to remove a bag that belonged to a passenger that decided to take a different flight.


Could the experience of inflatable structures in boats be applied to large aircraft design? Inflatable structures in boats have proved extremely successful and versatile since they began to find widespread use in the 1930s.

I'm aware that experiments have been made with inflatable wings - very light, delicate structures mainly on human-powered and unmanned aerial vehicles.

On boats, they're used differently: in some cases they form the main structure of the craft itself, in some, the craft has a rigid hull and the rest of the structure is inflatable, but either way, the inflatable sections are very far from delicate.

Experience gained with multiple air cells in inflatable engineering means that it's now possible to build effectively rigid structures, that are extremely tough, reliable and resilient. Their behaviour in failure modes is well-known.

Many large aircraft have built-in air compressors - the engines - that could keep the inflatable structures correctly pressured at all stages of a flight.

Materials science has produced enormous improvements in the longevity and resistance to chemicals/sunlight/temperature ranges of the rubber skins of inflatable structures.

What opportunities are there for designing parts of an aircraft as inflatable structures (perhaps winglets, or undercarriage doors)?

Is there any research or experimentation into more heavy-duty use of inflatable engineering in aircraft?

We now have experimental use of inflatables in space as well as for boats.

If an aircraft's engines are responsible for the inflation of any aerodynamic or structural part of the aircraft, however, one would have to answer what happens if the engines stop. A conventional aircraft whose engines fail at a sufficiently high altitude can glide for some time, giving the crew a chance to restart the engines; it may even be landed without engine power if necessary. This is a very bad time for the aircraft to lose aerodynamic performance or structural strength--for example, for the winglets to deflate just when the crew need the best possible glide slope.

Unlike boats or spacecraft, moreover, most conventional aircraft are intended to descend from altitudes of low pressure to altitudes of high pressure. If the amount of gas in an inflatable structure is held constant, one has to balance structural rigidity at low altitudes against the stress on the fabric from the much greater pressure difference at high altitudes. If the amount is not constant, it has to be replenished during descent. The engines cannot be relied on to do this, since the reason for descent may be engine failure. Gas could be supplied from high-pressure cylinders, but those can be heavy.

For an aircraft not intended to climb very high, these concerns are less severe.


Why would Boeing's MCAS be preferable to a modified Feel and Centering Unit? According to some sources, the purpose of MCAS on Boeing's 737 MAX variants is to increase the back-force needed to further raise the nose when flying manually at high angles of attack, in order to give the airplane acceptable handling characteristics when approaching a stall.

Both the MAX variants and their predecessors, however, already have an elevator Feel and Centering Unit (page 8), the purpose of which appears to be the generation of appropriate stick force feedback in all stages of flight. If so, then, at first sight, this would be the appropriate unit in which to implement the function of MCAS, raising the question of why MCAS would be the preferred solution.

A few possibilities have occurred to me, but they are just guesses:

MCAS functionality needs angle-of-attack input, which may not be available where the Feel and Centering Unit is located (in the tail), and it would be complicated to get that information to it.
This answer states the the Feel and Centering Unit is a mechanical computer; given that, it therefore might not be easily modified.
Modifying the Feel and Centering Unit would require re-certifying it in toto, not just its new feature.
In addition to modifying the handling characteristics, MCAS is also seen as contributing to stall prevention directly, by reducing the angle of attack.

NB: Recently, Dominic Gates wrote an informative article in the Seattle Times about the origins of MCAS.

On the 737 NG, at high angles of attack, the nose of the plane would naturally pitch down, helping to recover from a stall and to increase airspeed.

The larger engine nacelles on the 737 MAX are located forward of the center of gravity, which means that at high angles of attack they are pushing the nose up. MCAS helps to push the nose down in this situation, similar to how the 737 NG would behave.

The added nose down trim has the side effect of requiring more elevator input at high angles of attack, but that was not the primary purpose.

There are several reasons that the Feel and Centering Unit would have a difficult time providing similar functionality:

The airplane should pitch down even the absence of control input, so it could not be done by simply changing the way the elevators respond to pilot input.
MCAS takes input from angle of attack, altitude, flap position, and airspeed. The Feel and Centering Unit currently just senses airspeed, so it would somehow need to get the other inputs.
The Feel and Centering Unit is a mechanical computer, so adding new inputs and changing the behavior could be very complex to design and certify.

Another possibility would be to use the Mach Trim system to adjust the Feel and Centering Unit. The Mach Trim system uses the flight computer to adjust the elevator neutral position to provide stability at higher speeds. While the flight computer should have all of the information needed, stabilizer trim provides much more control authority.


What is this plastic device inside the plane window? I saw this on a recent domestic flight. It was glued on all the windows of the plane, behind the first layer of plastic. What is it and its purpose?

I've found it on the 737, both the -800 and Max as far as I've looked. It's even noticeable from the outside.
The related patent from 2005 is US7267302B2 Window airflow damper. It solves an issue with severe window fogging. Basically it's a device that replaces the usual breather hole by putting the hole on top and covering it with a damper.
There is a blog post about it called New cabin window design & installation:

A new cabin window assy has been introduced due to the fogging problems we all encounter on the 737NG’s. The new cabin window assy has a breather hole at the TOP, compared to the bottom vent hole at the BOTTOM on the old panes.
The new window assemblies use thicker outer panes, redesigned seals with integral stiffening ring, and an airflow damper over the middle pane vent hole (...)


How precise must a pilot be when flying a holding pattern? When ATC asks a pilot to fly a holding pattern, he expects the airplane to stay at the required altitude in the sector of the holding pattern.

For the vertical direction, the question is straightforward: how much can the aircraft deviate from its assigned altitude?

For the horizontal direction, the question is more tricky: can the pilot fly a larger than standard holding pattern (lower turn rate, straight legs twice as long as expected)? What happens if on the contrary the pilot flies the pattern in less than 2 minutes?

Bonus question: what prevents the pilot flying an 8-shape instead of an oval one if he stays inside the holding pattern area?

EDIT: my question is really about the limits. It is obvious that a deviation of few millimeter or less than 10 seconds is OK, but at what point does it start to be not allowed (in other word, what is the precision required)?

To better understand the problem I want to address, my comprehension is that as long as you stay in the assigned sector, separation is ensured without any ATC intervention. Thus, I see no added value to be as precise as possible as long as you stay in the assigned sector. You may circle closer to the holding point, the separation will still be assured. But what happens if you fly farther away but still in the assigned sector? And what happens if you fly a non standard shape but still inside the assigned the assigned sector?

Flying holds does not have to be rocket science and the holds do not have to be perfect ovals.  In fact when applying proper wind correction the pattern will not be a perfect oval.  There are two main parameters you need to meet to be safe and keep ATC happy when flying a holding pattern:

Maintain your altitude:  Sometimes an ATC controller will assign multiple aircraft to a published hold but assign different altitudes.  Any deviation of altitude could reduce separation to unsafe levels.
Stay on the cleared side of the hold as much as possible:  While there is some leeway if you cross over to the uncleared side (parallel entries typically do cross over to the uncleared side) you want to stay on the cleared side as much as possible.  This not only helps with separation of traffic and terrain but also helps keep you from drifting away from the fix especially if you are encountering winds aloft.

As far as your question concerning the time it takes to fly a holding pattern that is not that important as long as you are not drifting away from the fix.  Lets say you have a tailwind when flying towards the holding fix which will turn into a headwind when turning outbound.  The goal you want to obtain is 1 minute inbound legs.  But to maintain that you will need to increase you time on the outbound leg since you are flying into a headwind and losing ground speed.  That means your holding pattern will take longer to complete but ATC will not care about that.  ATC wants you to keep you altitude and not drift away from the fix.  Whatever you have to do to safely make that happen is fine with them.

Question about 8 shaped oval:  I assume you are talking about if you accidentally turn into the uncleared side of the holding pattern and fly a figure 8 to get back on course and how to avoid that.  The rule of thumb is apply two or three times the amount of wind correction on the inbound course to the outbound course.  The reason this is done to account for the difference in turning radius when turning into the wind versus turning away from the wind.  The resulting pattern will not be a perfect oval but will look like the pattern below.  (Image borrowed from this math stack exchange post).

If you would like more info on what airspace ATC actually expects you to use for a hold click here and see wbeard52's answer.


Does a flight briefer require a license in the US? Flight briefers have to stay on top of a lot of different variables. In order to give a pilot the information they need for their flight they must be able to interpret weather forecasts, keep on top of any ATC delays, and wade through all the NOTAM's to find the ones relevant to the flight plan.

The skill set overlaps with those of flight dispatchers. In the US flight dispatchers are required to have a certificate. Are flight briefers required to have a license or certification, either a dispatcher certificate or some other credentials?

I imagine that the do receive plenty of training and I belive there was a time where they were "Flight Service Specialists" (this may have changed when LM took over). The FAA offers a great free course through their WINGS program on Flight Briefings and how they work on the other side (from the briefers stand point). I attended it recently and I recall that the woman giving the course was a former briefer and was a Flight Watch Specialist. I don't recall if that was a requirement or not thought (you can always reach out to her and ask). It should be noted that Flight Watch/Lockheed Martin Flight Services are now run by Lockheed Martin on contract to the government and are no longer run solely by the government as they once were, which may have changed things operationally (I have only ever known it in its current state).

As for staying on top of things, in todays modern times that is more the job of a computer than the briefer. Things like NOTAMS and AIRMETS/SIGMETS in route are given to them digitally once you tell them your course/route. There was once a time when this would have been a manual process but those days have long since passed. In my general experience flying VFR on a longer flight the briefer will not give you all the radio outage NOTAMS up front but will ask you if you "want to hear the radio nav aid notams" or something like that. They will give you things with in a certain distance from your planned route or if you ask for it. For example you can say "is VOR XXX in service?" and they will look it up for you.

Other Notes:

There is an interesting discussion on the day to day here.
You can read up on the history here.
And this Article


Are go-arounds prohibited at St Barth (TFFJ)? The description of this video claims that past a certain point — which is around the turn to final — on approach to TFFJ (St. Barth) runway 28, a go-around is prohibited. That sounds strange. I understand how going around might be impossible past a certain point at VNLK (Lukla) or LFLJ (Courchevel), because the hill ahead is too steep to outclimb and too close to turn away from. But while there is a small hill beyond this runway too, it should be low enough to outclimb to much further. So:

Is a go-around prohibited past a certain point on approach to TFFJ runway 28?
If yes, it is prohibited from as early as the video suggests (around final turn, still well above the hill beyond the runway)?
And if yes, what are the reasons for it?

The video's description reads:

  After passing Eden Rock (min 02:39) it is prohibited to conduct a Go Around.

Below is at 2:39:

The official eAIP reads (link may die):

  AD 2 TFFJ.AD 2.22 Flight procedures

  22.2 Arrival flights:
  RWY 28:

  Going around is prohibited in short final.

If Eden Rock is that tiny island on the left, then it makes sense as the plane would be aligned and on short final after passing it, where a right break option is no longer available.

So the answer to the first two questions is yes.

The reasons are not on the chart, so possibly the clearance gradient was not met, was not demonstrated, or the risk to the road and community past the tiny hill is too high.

Also note AD 2 TFFJ.AD 2.21:

  Take-offs on RWY 28 prohibited.

(eAIP chart)


Where can I find documentation that state sales tax was paid in the 1980s when an aircraft was purchased? I am going from a sole owner to a partnership with two others in a Cherokee 140.  The state wants proof that state sales tax was paid in the 1980s when a family member originally purchased the airplane.

I have informally been a partner in the airplane since that time and have been paying half the bills. My partner recently passed away. I'm sure the state sales tax was paid but cannot find any documentation. They won't process the new registration until I can provide documentation that the state sales tax was paid, or I have to pay the fee again.

Where can I find a record that the state sales tax was paid when the aircraft was originally purchased by my family member?

This is a state level issue (here in the US) and you will have to contact the state in question. While aircraft are registered federally the sales tax is state imposed (and collected). If the family does not have the documentation you may have to go through some hoops to get it. Its also important to add what state you are in as that may change the answer to the question.

Furthermore depending on how you are setting up the new partnership there are tax implications to that as well. You should talk to a lawyer about the various ways this can impact things. Unfortunately in the eyes of the state you had no stake in the plane (despite your informal ownership, the state is only worried about formal ownership).


Why does the B-52 have such a tiny rudder? The B-52 (aka Stratofortress, aka Grey Lady, aka BUFF) has a minuscule rudder for an aircraft of its size and wing-mounted engine placement:

Compare to, for instance, the rudder on a 747:

The B-52’s rudder is so small that it can’t be used to decrab the aircraft during a crosswind landing, meaning that it had to be designed to stay crabbed throughout the landing roll, forcing the designers to use a fully-steerable dual-bicycle landing gear layout (plus wingtip outrigger gears that are there solely to keep it from tipping over) instead of the conventional tricycle arrangement.

Why, then, did the B-52’s designers give it such a small rudder?  One could argue that, because it has four engines on each side, rather than one or two or three, it doesn’t need a large rudder, because the thrust differential (and, thus, yawing moment) in the event of an engine failure would be minimal).  However, if you look more closely, that argument doesn’t hold up, because the B-52’s eight engines are mounted in conjoined pods, two engines per pylon, which virtually guarantees that an engine failure will also take out the engine right next to it;1 thus, one would expect that the design case for the B-52’s rudder would be a double engine failure of both engines on one pylon, rather than the improbable case of one engine failing and somehow managing to leave the one next to it completely intact.  So why isn’t the B-52’s rudder bigger?

1: For instance, the danger of cascading engine failures is one of the main reasons why no airliner designed after 1960 has ever used conjoined engine pods.

There are two reasons and they date back to the early designs for the aircraft. Keep in mind the tail is different now than when it was originally designed. Boeing has originally planned for an all moving vertical stabilizer but engineers doubted its reliability and the systems to operate it simply would not fit in the tail at the time. More importantly the original designs had sufficiently larger control tabs but this lead to an elevators and a rudder that had a lower critical mach number than the wing (i.e. the empennage would stall first). The engineers shortened everything to create a more stable situation as is noted in this passage:

  Concerning the rudder, the situation is much worse. The B-52 rudder
  and elevator have an exceptionally narrow chord. Most airplanes have
  at least a 25% chord, which allows sufficient power and effectiveness
  in both yaw and pitch during takeoff, landing, and asymmetric
  conditions. The same is not true of the B-52 with its 10% chord rudder
  and elevator. The chord was reduced because original designs of the
  aircraft had the tail exceeding critical Mach prior to the wing. The
  chord of the tail was reduced to ensure that the wing reached critical
  Mach first.[15]

  The original designers knew that the rudder was underpowered. An
  aircraft the size of the B‑52 requires a massive rudder that does not
  exist. This rudder is insufficient for the basic needs of the
  aircraft, let alone for asymmetric engine-out scenarios. Original
  plans called for an all moving vertical tail, the first of its kind.
  However, Boeing doubted the reliability of the hydraulic actuators
  necessary to achieve this. The design was also too heavy for the tail
  structure to sustain. Therefore, Boeing designed, built, and
  incorporated the yaw-adjustable cross-wind landing gear,[16] what is
  known to B‑52 aviators as ‘cross-wind crab.’ This system allows the
  B-52 to operate during normal conditions of take-off and landing in
  crosswinds. However, the true problem was asymmetry.


Why do planes above FL290 need more vertical spacing? At altitudes no higher than 29,000 feet, planes need only 1,000 feet of vertical separation.
However, planes over FL290 need twice that, i.e. they need 2,000 feet of vertical spacing between them and a plane with otherwise insufficient lateral separation.
Why is the extra vertical spacing needed, and why is it needed over FL290 specifically?

The atmospheric pressure changes more rapidly with altitude near the ground than it does higher up.  Assuming an instrument has some error based on determining the difference between two pressures, this error increases with altitude.

Using a standard atmosphere, the pressure difference between 3000 and 4000 feet is 3.3 kPa.  The difference between FL290 and FL300 is 1.4 kPa, less than half.


What causes a slight increases in indicated stall speed with altitude? Theorectically, the stall speed in IAS doesn't change with altitude, but this graph above shows the stall speed actually starts to increase a little from above a certain altitude. How can this be explained? Is it something to do with a compressibility effect?

The U-2C (which the graph is for) had a stall speed of about 79 KEAS, that is 79 knots equivalent airspeed (EAS) at all altitudes. At 50000ft, 79 KEAS is about 80 KIAS (indicated airspeed), but at 75000ft, 79 KEAS is about 83 KIAS. This is simply a consequence of the way that indicated airspeed is measured by pitot-static systems - the measured speed is not quite a true representation of the effect of the airflow upon the airframe. So, the apparent increase in stall speed is just an artefact of the way airspeed is measured, rather than the performance of the airframe itself.

You can confirm the EAS/IAS conversions for yourself using the Hochwarth Aviation Calculator.


Is the ILS CAT III system the most complex landing system available? Is the ILS CAT III the most technologically sophisticated navigation / landing  system available for helping commercial pilots land a commercial passenger aircraft in severe and extremely low visibility weather conditions. Does the airport require special compatible equipment for this system to work properly?

Yes ILS equipment for CATIII is the most sophisticated across ILS systems. As people mentioned in comments there are another types of landing systems, which could be more complex.
No it is not auto landing system.

It self CATIII is a category of a landing conditions.

Also take a look here What is different between a Cat IIIA, Cat IIIB, and Cat IIIC ILS approach?


Why would seaplanes use a curved takeoff run? I came across this interesting factoid in another SE Aviation answer (How flat does a runway need to be?):

  seaplanes often use a curved takeoff run.

I'm trying to imagine why but cannot come up with a good reason.

Does anyone know why?

Years ago now I gave a fair amount of instruction for seaplane ratings. I remember it quite fondly as seaplanes combine the fun of flying with aspects of the fun of boating. There were three conditions in which we used curved takeoff runs.

The most frequent curved takeoffs were on rivers, which tend to not run in a straight line, and even for those portions of a river that do, there may be rapids to stay clear of, so following the bend of a river or weaving between rapids was not unusual. In my case, the rivers were the McKenzie and Willamette, both in Oregon, USA. If you're ever in Eugene, Oregon, go down to Skinner's Butte Park on the Willamette River. On the upstream end of the park is the Ferry Street bridge. On the downstream end is the Washington-Jefferson bridge. In the 1970s we used to operate on the water between them, avoiding the rapids. We stored the airplane for a time on the Skinner's Butte Park shore line. That was legal and safe back then.

The next most frequent usage of curved takeoffs was to get off ponds that were not wide enough to allow a straight line takeoff. However, you can do it taking off in a curve along the perimeter of the pond. If you ever happen to fly over Daniels Field alongside Interstate 5 about 20 miles north of Eugene, Oregon, you'll see a lake/pond alongside the runway with a small island in the middle. There is no straight line you can draw on that pond that comfortably gives you room for takeoff, but you can circle the island and get into the air without difficulty.

The third circumstance we didn't have to use often was when we had to run across our own wake to be able to get up on the step on glassy water. For example, Waldo Lake in the Oregon Cascades is at 5,400 feet elevation. A J-3 cub with an 85 horse engine and with two people on board simply cannot get up on the step when the surface of the lake is a dead calm. However, if you get going in a curved path, you can get up on the step when you run across your own wake. Once you're on the step, you can then put the airplane up on one float and get enough airspeed to take off. Just as a matter of information, seaplane operation on Waldo Lake is now prohibited.


What is the make and model of this biplane? This photo is of one of my friend's great grandfather:

We wish to commemorate a museum in his name as he was a highly regarded person in his area, so we wish to show this photo in the museum with details of the plane.

It's a De Havilland DH.83 Fox Moth

 Source Wikipedia. Photographer:  Chris Finney
With a bit of image contrast and brightness modification, the registration can be read on the underside of the wing: VT-AEA.
VT is the registration prefix for India since the 1930's
The historic registration can be found on www.airhistory.org.uk and here.

Registr.
Type
Serial #
Reg. History
Owners
Date
Cert. #
Fate

VT-AEA
DH.83 Fox Moth
4043

The Bombay Flying Club Ltd
01.05.33
173
Reregistered 6.12.37

VT-AEA
DH.83 Fox Moth
4043
VT-AEA
GB Keshein, Bombay
6.12.37
173/2
Reregistered 1.2.38

VT-AEA
DH.83 Fox Moth
4043
VT-AEA
Air Services of India Ltd, Bombay
1.2.38
173/3
Cancelled 10.7.41

The aircraft was first owned by the Flying club of Bombay since 1933, then briefly by G.B. Keshein in Bombay and then by Air Services of India until 1941.


What is the overhead instrument panel (pictured) near the front galley area of an A320? I have noticed this overhead instrument panel. It is convered by a transparent plastic lid with a small hole in the middle. Inside it has lot of switches. What is it supposed to do and who operates the same?

I couldn't find an exact picture, but the below image highlights the area where the panel is:

Image Source

(easamodul10.blogspot.com)

That panel you saw is the forward cabin circuit breaker panel. There is also an aft one.

It is used by maintenance personnel and cabin crew. For example if a toilet becomes inoperative, pulling the 'vacuum sys C/B' for 30 seconds might solve the issue.


Which specific version of English are international pilots and ATC required/recommended to learn? Are international ATC and pilots technically required to learn British English, American English, or something else? I've heard it said that they are "supposed to speak ICAO standard phraseology, which just happens to be made up of English words," and that many ATC and pilots speak precisely as many English words as they need to scrape by. Even if they aren't explicitly required to speak AmE or BrE, they are still indirectly required to speak whichever version ICAO standard phraseology is based on, so if that is the case, which version would this be?

Some other things that I'm not asking about directly but might be helpful in providing a complete answer: a bit more about ICAO standard phraseology - is it considered a separate "controlled language" like Simplified Technical English, which was incidentally (or maybe not) developed for use in aviation maintenance manuals? Is it a subset of STE?

The FAA bases English proficiency on the ICAO Level 4 English Language Proficiency Criteria, which don't mention any particular dialect or variant of English. Instead, they focus on the speaker's ability to communicate and they explicitly accept that the speaker may make mistakes (emphasis mine):

  Pronunciation, stress, rhythm, and intonation are influenced by the
  applicant’s first language, but only sometimes interfere with ease
  of understanding.
  [...]
  Basic grammatical structures and sentence patterns are used creatively
  and are usually well controlled by the applicant. Errors may
  occur, particularly in unusual or unexpected circumstances, but
  rarely interfere with meaning.
  [...]
  There may be occasional loss of fluency [...] but this does not
  prevent effective communication

It's clear that ICAO doesn't expect non-native speakers to be fully fluent, and once you accept that then there's no benefit at all in trying to enforce a particular dialect. Using standard vocabulary and phrases is the real key to effective technical communication, and you can see that in many other professional contexts too.

I've met plenty of non-English speakers who can speak effectively but not fluently about a specific technical domain, but they still don't have the vocabulary to talk about their holiday plans or other 'trivial' topics. Asking what dialect of English those people speak is fairly meaningless, but Globish might be the best answer :-)


What is recurrent training? Is it taken by both pilots and flight attendants? How frequently? What is the main purpose of it? Is it mandatory?

Recurrent training is required annually by the FAA for both pilots and cabin crews, by 14 CFR 121.427.  I am only familiar with the content of recurrent training for flight attendants so this answer is limited to them only.  In a previous answer I wrote:

  Annually we would be required to attend jet recurrent training where we reviewed NTSB accident reports with an emphasis on cabin crew responses to emergencies, review of first aid and CPR techniques, re-testing of our knowledge of the location and how to use all the safety equipment on board, including life preservers, life rafts, and emergency slide procedures. We were also briefed on any changes to FAA mandated procedures and tested on everything.

The purpose of the training is to refresh our knowledge of required safety procedures that might have gotten rusty and to stay up to date on possible changes to FAA required procedures.  Emergency procedures are almost never needed and yet it's vital to be able to recall them when needed.  One day a year was devoted to recurrent training and you had to pass all the tests to stay current.  For this reason, we took it very seriously.


Does the nearest function on a G1000 allow for listing of anything other than nearest airports? In non G1000 GPS systems, I have seen several pages for selecting the nearest airport, VOR, NDB, intersections, and waypoint, but in a G1000, I can only seem to get a listing of the nearest airport, but have to manually enter VORs.

Am I missing something, or does the G1000 not have nearest functionality for these other categories of identifiers?

The G1000 and G500 do indeed have pages for the nearest VOR, NDB, Intersections, and user defined waypoints. The  G1000 Integrated Flight Deck Pilot’s Guide gives a list and flowchart / interface map for these.


Is there an online source of active flight plans? Is there a way I can look up flight plans filed in the United States? I tracked an aircraft on Flightradar24 and I would like to be able to find it's flight plan in some sort of database.

It seems you are looking for domestic flights in the US. The FAA database is not public.

You can use ADS-B tracking sites to look at the route. Remember instructions after takeoff (departure and transition) and before landing (transition and approach) are determined late and can be changed, depending on winds and other parameters.

E.g. on Flight Aware, for JBU124 between LAX and JFK, the route is mentioned:

and can be decoded:

These sites also create route history records. After a certain number of days, it's paying.


Does an heavy propeller aircraft (CS-25) have the Blu Line (Vyse) displayed on ASI? Does a propeller aircraft that is categorized as CS-25 (EASA Regulation) have the Blue Line (Vyse) mandatory displyed on ASI?
I know that would be the case for lighter aircraft (Less than 19000 lbs /8600kg), but my question is related for heavy aircraft (Dash8 example).

No, larger aircraft typically don't have such speeds shown on the ASI because they vary significantly with weight. See also Why don't Transport Category aircraft have a listed Vy?.

For the Dash-8 Q400 for example, the $V_{\text{y}_\text{SE}}$ speed is called $V_\text{CLIMB}$:

  VCLIMB – Single-engine best rate-of-climb speed.

The following table shows the values for $V_\text{CLIMB}$ as a function of weight:

+-----------+--------+
|  Weight   | VCLIMB |
+-----------+--------+
| 18.000 kg | 130 kt |
| 20.000 kg | 131 kt |
| 22.000 kg | 137 kt |
| 24.000 kg | 143 kt |
| 26.000 kg | 148 kt |
| 28.000 kg | 154 kt |
| 29.000 kg | 158 kt |
+-----------+--------+

As you can see, the values vary too much to show a single blue line on the ASI.

This does not mean that the speed cannot be displayed at all. The Dash-8 Q400 has a Primary Flight Display (PFD) and can show up to 5 speed markers on the speed tape ($V_1$, $V_\text{R}$, $V_2$ and two more called #1 and #2, typically used for $V_\text{FRI}$ and $V_\text{CLIMB}$ respectively during takeoff and initial climb).

(Dash-8 Q400 FCOM - Indicating and Recording Systems)

The resulting markers on the PFD look like this:

(Dash-8 Q400 FCOM - Indicating and Recording Systems)

The electronic standby instrument does not show these markers.


How long can passengers survive after ditching in the ocean? Assuming Malaysia Airlines Flight 370 ditched in the ocean, and surviving passengers and crew were floating around in their inflatable vests, how long could they survive?

Is there data about the longest survival under such conditions?

There are a few examples of people surviving for months in tiny boats, but there they could gather rainwater and catch fish, obviously impossible in just a lifejacket.

Edit: although I mentioned a specific flight and lifejackets, the question is intended to be general for ditching in the ocean.

Well, your scenario is a bit unlikely because if the aircraft did ditch in the ocean they would have the emergency rafts and slides to take cover in instead of "floating around in their inflatable vests".

However, if someone were floating in the ocean without any protection, how long they could survive depends on various factors.  Temperature is the biggest factor in the amount of time before they would succumb to hypothermia.

Take a look at this chart to figure out the average temperature of the area in question.  If we go by the latest news, that is going to be somewhere in the neighborhood of 14C.

This page says that the Expected Time of Survival is 1 to 6 hours.

The same page also says:

  Maximize your chances of surviving by:

  Wearing a personal flotation device (PFD)
  Adopting a survival position
  Keeping clothing on
  Getting as much of body out of the water as possible
  Remaining still and in place UNLESS a floating object, another person, or the shore is nearby
  Keeping a positive mental outlook (a will to survive really does matter)

  Swimming isn't recommended unless there is little chance of being
  rescued and shore is less than a mile away. Putting on a PFD after
  falling into cold water is almost impossible – SO WEAR IT. If you find
  yourself in cold water without a PFD and nothing to climb onto, tread
  water. Traditional drown-proofing by repeatedly lowering your head
  into the water and floating speeds up heat loss.

Lots more information is available on that page!


What are the holes on the top side of the canard of Eurofighter Typhoon for? The Eurofighter Canard has some holes on top side. What are these holes for?

?

They aren't holes they're flush screw heads.


How can I calculate the relationship between propeller pitch and thrust? I am trying to design a WWI propeller so I started calculating. The propeller comes with a specified pitch of 1.75m. The engine is supposed to run at around 1900 rpm and 147kW. These are most likely not the maximums, but I use these values as a starting point.

So I calculated the propeller speed: 1900/60 * 1.75 * 3.6 = 199.5 km/h

I also found on the internet an angle of 16.88 degrees but the site mentions "angle of attack" which I deem incorrect. However if I treat the value as "effective pitch angle" I get about the same speed of ~195.68 km/h (using the formula from Koyovis for Φ from How to calculate variable pitch propeller parameters?).

Everything looks good, my reasoning at this point is that this prop is suitable to be used for the particular aircraft. The speed that I found seems to be reasonable for this aircraft.

But here comes the problem, this is the part that I don't understand and that is 'thrust': if the propeller reaches 1.75 pitch this means that the exit velocity - the input velocity (Ve - V0) is 0!

If I understand the formulas (such as here) correctly this means there can no longer be thrust. How would it possible then that the aircraft is still being pulled forward? This automatically means the aircraft has to slow down. But my assumption is that the propeller is 'designed' to go as fast as the specified pitch.

Can someone enlighten me please. Why does my propeller have to be slower than designed?

edit (I will leave my question above unaltered).
Clarification as per request of JZYL:

The propeller is: AB622
Some of these propellers can still be found on auction sites and such. They have markings like "G 1669 NO 90 DRG AB 662 CRH HISPANO SUIZA, WOLDSLEY VIPER D2400 M/M p 1750 2400mm"

The pitch is 1750mm
The diameter is 2400mm

The aircraft I am looking at is a WWI SE5a with a Wolseley W.4A Viper engine.
It is difficult to state exact parameters. There is a lot of 'belief' of what the aircraft at that time could do.
Some people say the aircraft top speed would be 138 mph (220 km/h). However might as well be one top speed ever recorderd for one plane at excellent flying contditions. Also some people claim the engine could run at 2200 RPM.

So instead I go for some 'safe' or nominal values:
Speed = 125 mph
RPM = 1900

The calculations that I make do not add up. The "pitch speed" (I don't know what the official term is) that I have calculated for the prop is 199.5 km/h (124.6 mph) with these parameters.

But if I have to take slip of say 10% into account (how much is normal, 5% 10%?).
In that case I go down to: 112 mph.

112 mph is way below what people see as the maximum speed of the craft.

So I am basically trying to find a clarification for this.

The geometric pitch ($p$) is simply the distance that a point on the prop would move forward in one rotation, if it's gripping in a solid medium. You can derive the pitch speed via this geometric relation if you wish, but I would caution against inferring performance from this number. Instead, you should consult propeller, engine and aircraft performance in their entirety.

Using your provided data, let's see if everything fits. We assume:

Prop RPM of 2200
Top cruise speed ($V$) of 125mph
Prop diameter ($D$) of 2.36m (from Wikipedia on SE5a)
Prop pitch ($p$) of 1.75m
Wing area ($S$) of 22.7 sq.m (from Wikipedia on SE5a)

From this reference, the reference pitch angle/blade angle ($\theta$) by convention is measured at 3/4 of the blade radius, and can be related to pitch via:

$$\theta=\tan^{-1}{\frac{4}{3} \frac{p}{\pi D}} \approx 17.5deg$$

The advance ratio is calculated, with $n$ being the prop rate of rotation in round per seconds:

$$J=\frac{V}{nD} \approx 0.65$$

Using the plot below as a rough reference, which is predicted for the McCauley 7557 propeller, gives a thrust coefficient ($C_T$) of 0.06.

Ref: http://webserver.dmt.upm.es/~isidoro/bk3/c17/Propellers.pdf

Now the thrust coefficient is defined as:

$$C_T=\frac{T}{\rho n^2 D^4}$$

where $rho$ is the air density and $T$ is the propeller thrust.

For level flight, thrust equals drag, and we can back calculate the drag coefficient:

$$C_D=\frac{2C_T n^2 D^4}{V^2S} \approx 0.07$$

This is high enough to be well within the realm of possibility for a biplane (if it's too low, then it's an indication that the performance numbers do not jive). For reference, Cessna 172 has a total drag coefficient of 0.032 at 122kt at SL. In conclusion, I would say that your numbers check out in the back-of-envelope sense.


Why weren't the Airbus A330 engines designed with a system to stop their fans? Why wasn't the Airbus A330 designed to stop its fans (with some kind of 'handbrake')?

To clarify, I am specifically talking about the aircraft that flew Air Asia flight D7237.

During the flight the aircraft suffered from a fan blade separation event and the the result was that the engine became unbalanced.

This was the result of the incident the plane was able to continue flying for over an hour and a half with the "moderate" vibrations and able to land safely (where the passengers were rewarded with a $20 voucher)

It's my understanding that the engine was immediately shut down, and that the cause of the vibrations was the fanblades freely turning as the plane moved very fast through the air (similar to blowing very hard into a turned off household fan)

But to me, it seems the whole situation could have been avoided if there was simply some kind of "brake" or 'locking' feature that prevented the fanblades from turning freely in the wind.

I feel as though there wouldn't exist another scenario where a plane could possibly experience more severe, prolonged vibrations than a windmilling event, and the windmilling event itself could be prevented if there was simply a way to lock the fanblades from moving freely.

The reason I say A330s in particular is because I am not aware of the features of every other jetliner, although I am aware some propeller engines can feather their blade parallel to the direction of airflow to prevent this.

Complexity and weight, what airlines hate most.

Has it been done before? Yup. A variant of the Convair B-36 Peacemaker was able to stop the windmilling when the jet engines were not needed (that variant had 6 piston engines and 4 jet engines).

(Source)

  The metal petals filling the inlet prevented the jets from turning in the wind as the B-36 cruised for long periods of time with them turned off. The petals retracted to allow the jet engines to be ignited for extra thrust during take-off and high speed dashes. A strut braces the nacelle against swinging from side-to-side.

Scaling this up for the big diameter engines for that very rare engine failure is not cost effective. Instead planes can survive, and are extensively tested for, vibration and flutter.

How rare is very rare?

  By the 1970s, advancing technology had set the stage for two-engine, turbine-powered airplanes to safely exceed the 60-min operating restriction [away from the nearest airport]. The result was ETOPS, which began in 1985 with 120-min diversion authority and the requirement for an average engine in-flight shutdown (IFSD) rate of just 0.05 per 1,000 engine-hours. With 180-min ETOPS authority, which followed in 1988, an even more stringent reliability target of just 0.02 IFSDs per 1,000 engine-hours was specified (Boeing, 2003).


Is there a good reason to have a handheld Aviation Microphone in GA? I have a Cessna 172P in which the handheld microphone has stopped working. Before I replace, I was wondering if there is any good reason to even have one? I have PTTs on both the pilot and copilot, yoke.

According to the 172 Minimum Equipment List from Cessna (S and R models)

these are both Category C items which the MEL states

  Category C: Items in this category shall be rectified within ten (10) calendar
  days, excluding the day of discovery.

So it looks like you may need to fix it but in the event you are flying it looks like you need an alternative (headset should do that) and or a backup headset on hand.

However the 4th column states that zero are required for dispatch so you can fly without it.

As people are noting in the comments in a lot of planes these mic's go more or less unused or are inop these days. I know I have never personally used one in any of the archers I have flown.


How should passengers report SOS signal sightings? On January 23, 2015, I flew from Buenos Aires, Argentina (SAEZ) to Santiago, Chile (SCEL). It was a very comfortable night flight in a Boeing 787 Dreamliner of LAN airlines, though it was delayed.

During the descent and a pronounced turn to the left at approximately 4,000ft above the Andes Mountains, I saw through the window a wood fire in the middle of darkness with some shadows around. Then a brilliant white light blinking: three short flashes, three long flashes, three short flashes. I thought: Wow! That antenna blinked like an SOS signal!

One second after the first sequence, again: three short, three long, three short. Then I unfastened the security belt to run and tell the closest flight attendant: Sir! There is an SOS signal there, and he started to give attention to it.

After a successful landing on runway 17 L/R, I asked the flight attendant if they have a procedure to handle this kind of sightings. He told me there is no such procedure and that I should go to inform the civil protection office.

Due to a lack of enough time before the next flight, I asked a security officer to inform the civil protection office, giving her the flight number, exact time of the sighting and after calling the person in charge, she asked me for my name and details about the sighting. Trying to be descriptive, I clearly told her all details before running to catch the next flight and almost losing it.

How should passengers report SOS signal sightings?

P.S. The place of sighting was somewhere over the mountains in the west of Los Andes in Chile.

There is a procedure, at least for the aircraft crew.

It is appropriate for a flight crew to transmit a "pan pan" or even a "mayday relay" so a passenger should immediately inform the senior cabin crew member, usually by asking to  speak to the "purser".  SOS is an internationally recognised distress signal.  If the purser did not act upon it, I would politely, but assertively request that they inform the captain since these procedures are part of standard pilot training and flight crews are required to respond to potentially life threatening situations.

Reporting emergencies or urgent situations is not restricted to the aircraft itself.  It can, and should be used, where any threat to life or safety  is real or possible.  ATC in turn can contact the appropriate local resources depending on the situation.

An example would be if I was flying and witnessed a fire or perhaps a road crash and emergency services were not already in attendance, I would not hesitate
to contact ATC and be prepared to offer assistance if possible, for example relaying position or exact circumstances.

You did the right thing.  Perhaps you could have been a bit more assertive at the time, when the cabin crew member incorrectly told you that there is no procedure, since minutes can count.


Are you required to report leaving an altitude if you have been given a crossing restriction? If ATC gives me a clearance to cross a fix at a specific altitude or a descent at pilot's discretion and I read back the clearance, is my readback considered the report specified in the AIM, or do I have to inform them when I actually start down?

  AIM 5-3-3. Additional Reports

  a. The following reports should be made to ATC or FSS facilities
  without a specific ATC request:

  1. At all times.

  (a) When vacating any previously assigned altitude or flight level for
  a newly assigned altitude or flight level.

  ...

An Example - Say that a pilot is flying at flight level 340 100 NM from Wilmington VOR and gets the following clearance:

  ATC: N1234, cross Wilmington VOR at flight level 240
  Pilot: Cross Wilmington VOR at flight level 240, N1234

or

  ATC: N1234, descend at pilot's discretion to flight level 240
  Pilot: Descend at pilot's discretion to flight level 240

It's a little early to start down since we want to stay high for fuel efficiency, so the pilot decides to wait until 30 NM from the VOR to start down.  When they reach that point, are they required to inform ATC before starting the descent or are they considered to have reported the descent earlier?

I hear pilots that do it both ways and each camp is pretty emphatic about it....

I’ve been a controller in both the en route and terminal environments. While I agree with your interpretation of the AIM that it appears to be required, reorting leaving your altitude is not expected and I did not usually hear it done.

To give the perspective from the other side of the mic, an altitude crossing restriction is functionally equivalent to a pilot’s discretion climb/descent to that point. ATC will protect all altitudes between your current one and the restriction, and you are free to hit that restriction as you see fit (barring the violation of other regulations, of course). You may not return to a previously vacated altitude as part of your climb/descent, but you may level.

You are also correct in that it can tie up the freq as an “unnecessary” call, but if you are unsure, better to over inform rather than under inform.

Incidentally, very few controllers read the AIM. The 7110.65 takes precedence, and I’ve actually had a supervisor yell at me for referring to the AIM once. I know, I know.

So, legally, it should be done.  In practice? Unnecessary and I preferred that it not be done when I was working.


Could the US Air Force ever replace the Thunderbird pilots with drones? Would it be possible or practical for the US Air Force to replace the Thunderbird pilots with drones?  The drones could perform more difficult maneuvers and do them more precisely.

The University of Pennsylvania is successfully working on small-scale formation flying.

Tight formation flying can be done with stock aircraft and skilled pilots, but drones would need additional sensors and new code in their FCS. Also, you can fly aerobatics even with gliders, but only when a decent power-to-weight ratio is reached, aerobatics becomes a spectator sport. I think it is frivolous for the US Air Force to pay for the development and additional equipment to make drones fly aerobatic displays, but few Air Forces are known for an enlightened budget discipline. I expect, however, that this will be added first by a company producing drones, and for demonstration and marketing purposes, and then the taxpayer will fund this indirectly.

Formation flying was a needed skill for bomber pilots, back then when their bundled defensive weapons provided the best protection against fighter attacks, and aerobatic flying was and still is valuable for fighter pilots. In the days of missiles and UAVs, neither formation flying nor aerobatics are necessary skills anymore, so in a way aerobatic formations are a quaint relic from the last millennium.

To answer the "could" aspect of your question: No, not directly. This would need modifications to existing drones.

To answer the "ever" aspect: Once the services field UCAVs (unmanned combat drones) with a good power-to-weight ratio, having them fly aerobatic displays looks almost unavoidable, but I expect it will not be the Air Force, but the marketing department of a big contractor driving this.


What is the power rating of the ground power unit for Bombardier Dash 8 Q400? I am researching about ground power units for aircrafts and I need the power rating requirements (kW/kVA rating) of ground power units to supply electrical power to Bombardier Dash 8 Q400 and Embraer E145.

I know that aircraft need 115VAC and 28VDC, but I need the power rating of the GPU in kW or kVA like an Airbus aircraft needs a minimum of 90kVA GPU.

Specific information about requirements is difficult to find. However there is some information that is readily available concerning the Q400 and available ground power units.

The Q400 can start its engine with the onboard batteries, thus the necessary power requirement would not be nearly as big as with the A320 series.
Ground Power Units are usually supplied in 7,5, 15, 30, 60, 90, 120, 150 and 180kVA configurations
The Q400 is listed to have two TRUs which can output maximum of 300A 28VDC from a 115VAC (~73A) source. Source: Q400 Eletrical This would equal to a 90kVA Ground Power Unit, which according to Power Systems International provides 72A.
The Q400 has one 45kVA electrical generator per turbojet.
According to the Q400 Electrical document the Q400 has 24-volt NiCad batteries; Main and auxiliary, which both total to 80Ah.
The same document also states that the Q400 External Power Protection Unit does not monitor amperage, thus will not monitor total power. Some other system related with engine starting will most likely still monitor total power.
Aviation New Zealand provides the following details:

  "Small business jets fitted with 115 V 3 phase systems may be supplied by lower
  power units, typically 7.5 kVA and 15 kVA. Aside from over-power limits, all other
  parameters are likely to be similar to the above. " above=minimum 45kVA (as according to the document is specified in
  ISO 6858:1982 (E): Aircraft Ground Support Electrical Supplies – General
  Requirements;)

Based on these details I think that the Q400 does not have specific external power requirements. Most likely a minimum of 7.5kVA is still recommended, as that is the lowest powered GPU I could find. However you might end up charging the batteries first, as the 7kW from the GPU might not be enough to start the engines. A 30kVA generator with 150% overload rating for 60 seconds is also most definitely enough since it can provide the exact 45kVA that is provided by the generators already in the engines of the Q400.

The best guestimate calculation I could come up of what the engines need to be started is:

  A320 CFM56 provides about 30000hp max, while the PW100 provides about
  5000HP
      The CFM56 is started by a APS3200 APU, which provides 447hp, of which about 330hp can be used by the compressor equaling to about
  240kW.
      Based on the hp difference of about 15%, we will assume the PW100 requires
      only 15% of that power to start, which would be 36kW or ~40kVa.
      Of course not all of the 240kW provided by APS3200 would be required for a     CFM56 to start, so I'm pretty confident that a Q400 engine will start with a 30kVa GPU.

I think in the end it might come up to the question of using the batteries more, thus them needing more maintenance. NiCd usually rated to 1500-2000 recharge cycles, on Q400 and aircraft batteries it is most likely even lower.


Why is there a provision of pressure setting in GPS? Some of the GPS have a provision of setting barometric pressure (QNH/QFE). How does it work?

By either manually entering the indicated altitude, total air temperature, barometric pressure, etc., or feeding those variables via sensors connected to the GNSS unit, it is able to know the true airspeed, wind direction/speed and the head/tail wind components.

Very useful for knowing the performance in-flight.

Example interface for the Garmin GTN 650/750 series with software 4.10:


If an A/C have Radio failure ( sqk 7600 ) How the ATC will give him instruction or how will he land? If an A/C have Radio failure ( sqk 7600 )
How the ATC will give him instruction or how will he land ?!

This is a question with many answers, depending on the conditions of the flight. Let me limit myself to private recreational aviation (what the FAA calls Part 91) in a single-engined propeller aircraft.

If you are flying Visual Flight Rules (VFR), there are some airspaces you need to stay out of. For instance, US and Canadian Class B and C airspaces require radio communication. You won't be able to land at airports in such airspaces without some other arrangements.

You can give a signal that you are lacking radio communication. Squawking 7600 on your transponder is one way. Flying a triangular pattern, which might be visible to ATC on radar, is another way. I have sometimes used my cell phone to call ATC's phone number.

Control towers in the US and Canada might well have "light guns": bright spotlights which the controller can point at an aircraft, and colour red or green, and shine continuous or blinking light. A continuous green light from tower to an aircraft preparing to land means that aircraft is cleared to land.

If you are flying Instrument Flight Rules (IFR), there are specific procedures to follow if you are unable to communicate with ATC.  Frequently they boil down to holding for a few minutes, then continuing on your flight planned route.

Remember that some aircraft have no electrical system, let alone radios. They fly, take off, and land just fine. There are many airfields with no control towers. There is uncontrolled airspace in which to fly. In these cases, pilots maintain safety by seeing and avoiding other aircraft. Pilots fly traffic patterns before landing, and sequence themselves cooperatively.  Lots of aviation works just fine without radio communication between pilots and ATC.


What is the role of a CFI (not CFII) as safety pilot for hood time? I am an instrument student at a flight school with a "primary" CFII whom I'm logging dual instruction time. Things are going pretty well, making progress but the instructor has been unavailable a bit more lately. Now, I also belong to a flying club next door at the same airport where the planes are much cheaper but double-I instructor availability is not as prevalent. My checkout instructor at this club has been giving me hood time. The rental cost of the plane at the club plus non double-I instructor time is actually more cost effective, and scheduling has been more of a breeze than getting dual time with the flight school's instructor. My flight school instructor looked at my logbook and did a double-take on a recent entry with the checkout instructor. I'm guessing he's not happy because I'm not doing business with his flight school 100% and renting their higher rate airplanes with a safety pilot (i.e. his other IR students). My double I is encouraging me to do some safety pilot time with other IR students, which obviously isn't a bad idea either for some folks. From my standpoint, I didn't want to do as much safety pilot time at the school since we trade off (i.e. I need 2x the amount of free time), and I figure I get the value-added of CFI coaching at the club. BTW this checkout CFI is about 1-2 months away from his double I and is actually signed off on giving me FTD dual instruction. Hopefully this makes sense so far...
I guess the questions that arise are: would this be a red flag for you as an instrument student? Is it really a big issue if a non-II CFI provides mentoring along with being a safety pilot for the simulated hours that is NOT dual instructor allocated (i.e. the other 25 hours)? Is the CFI in a legal bind somehow because they should "know better" if they let me as PIC do something wrong?

The bottom line is that it is up to you. It would be very beneficial to get as much simulated IFR time as possible. It does not matter if it is with your school CFII, a school student, the club CFI, a club student, or an unaffiliated and current pilot friend. Your CFII should not have a problem with that. Instruction (and the cost of it) is about you, not him. Although, they may have a legitimate concern about the quality of training you are receiving outside of the school. And, be wary of training in aircraft that are too different from one another, even in the same make and model.
The benefits of doing IFR time with your school CFII are:

It counts towards dual instruction time.
Your instruction stays consistent in structure.
The CFII will be able to give you the gouge (predisposition of questioning and testing) of the DPE.
The CFII is already familiar with your deficiencies.

The benefits of doing IFR time with the club CFI:

It counts as PIC and IFR time even if it does not count as dual instruction.
Costs less than the school.
You get a different perspective, tools, tips and tricks from an instructor qualified, instrument rated pilot.
A new/different set of eyes may uncover different deficiencies.
Typically, club instructors are going to stick around and have more longevity than school instructors. Although, this may not always be the case. It will give you an opportunity to build camaraderie and community for the future. After all, who is going to give you your Flight Reviews and Instrument Proficiency Checks.

The benefits of doing IFR time with another student:

Another student may have picked up something different but useful in training than you did.
Collaborative learning.
Building community and networking for the future.
Cuts out the cost of an instructor.
If it is a school student, their training will be consistent with yours (supposedly).
If it is a club student, they may have been trained completely differently. You may be able to glean useful tidbits from that different training.
You get to double your total flight/PIC time when trading off safety pilot-flying pilot responsibilities.
Flying! ‘Nough said.

The benefits of doing IFR time with a current and proficient, unaffiliated pilot friend:

Again, Flying! Flying is winning.
Totally different perspective. Remember, a good pilot is always learning, even from other pilots.
Camaraderie, community, networking, friendships, and that $100 burger/breakfast/BBQ.
You can fly any aircraft that you want. Although, it may not count as total and/or PIC time if you are not certificated for that category, class, and type rating if applicable unless the friend is also a CFI.
And of course, money. You can fly something cheap. Ty to find someone who owns their own aircraft.

Lastly, never overlook or underestimate the value of just sitting in the backseat with your headphones on and your mouth shut during another student’s lesson. You may pick up a lot of valuable information when you don’t have the added burden of flying the aircraft. Even if you can’t actually log the time.
As far as the “legal bind” that you mentioned. Any and all pilots acting as PIC will be in a legal bind if something goes wrong. After all, they are PIC for the purposes of safety of flight. That is the responsibility of their certificate. Any PIC who currently or in the future earns a living from their commercial license of any type will have more at stake than a recreational pilot.


Which airplanes are required to have a Flight Data Recorder in Europe? I know that not all aircraft are required to have a Flight Data Recorder (FDR) in Europe (for instance, a small single-engine airplane doesn't need one), but many are, and depending on the age of the aircraft different types may be required.

I've done some searching but am much more familiar with FAA rules and can't seem to find even the right place to look for the "official" answer.

When is an FDR required to fly to Europe in a foreign registered aircraft (FAA if it matters)? I am curious about the actual EASA FDR regulations which cover all aircraft (both private and commercial).

ICAO Annex 6 holds the answer.
For commercial aviation (annex 6 part I):

6.3.1.1 Types
6.3.1.1.1 Types I and IA FDR shall record the parameters required to determine accurately the aeroplane flight path, speed, attitude, engine power, configuration and operation.
6.3.1.1.2 Types II and IIA FDRs shall record the parameters required to determine accurately the aeroplane flight path, speed, attitude, engine power and configuration of lift and drag devices.
6.3.1.2 Operation
6.3.1.2.1 All turbine-engined aeroplanes of a maximum certificated take-off mass of 5 700 kg or less for which a type certificate is first issued on or after 1 January 2016 shall be equipped with:
a) a Type II FDR; or
b) a Class C AIR capable of recording flight path and speed parameters displayed to the pilot(s); or
c) an ADRS capable of recording the essential parameters defined in Table A8-3 of Appendix 8.
6.3.1.2.3 All aeroplanes of a maximum certificated take-off mass of over 27 000 kg for which the individual certificate of airworthiness is first issued on or after 1 January 1989 shall be equipped with a Type I FDR.
6.3.1.2.4 All aeroplanes of a maximum certificated take-off mass of over 5 700 kg, up to and including 27 000 kg, for which the individual certificate of airworthiness is first issued on or after 1 January 1989, shall be equipped with a Type II FDR.

For general aviation (annex 6 part II):

3.6.3.3 Flight data recorders - aeroplanes for which the individual certificate of airworthiness is first issued on or after January 1989
3.6.3.3.1 All aeroplanes of a maximum certificated take-off mass of over 27 000 kg shall be equipped with a Type I flight data recorder.
3.6.3.4 Flight data recorders - aeroplanes for which the individual certificate of airworthiness is first issued after i January 2005
All aeroplanes of a maximum certificated take-off mass of over 5 700 kg shall be equipped with a Type IA flight data recorder.

As rules and regulations tend to change from time to time, you should always check the latest edition of ICAO Annex 6 for current requirements.


What course should be taken to make estimated calculations? (skyvector.com)

When I want to calculate the leg time from GIJ to CRL going along the airway J554, at say FL190, I know that I have to calculate the ground speed first, but in order to do that, should I take 082° magnetic course, 087° magnetic course (reciprocal of 267° from CRL), or should I enter in the CX-2 flight computer (Plan Leg) an average of them?

What I would normally do is to enter in the CX-2 flight computer the true course (calculated with a plotter) in order to get the ground speed; but I want to know if it is correct to get the true course by converting the known (shown on the chart) magnetic course by adding or subtracting to it the magnetic variation, whatever be the case.

In this case the magnetic variation around GIJ is 1W and the magnetic variation around CRL is 3W, so the true course of the GIJ - BENJO - CRL leg would be 81° and 84°, am I correct? Once again I get confused without knowing if I should take true course 81°, 84° or an average of both.

In the explanations given in the FAA book ATP Test Prep, relative to the nav questions in the performance chapter, the course to be taken, is sometimes the magnetic course that corresponds to the beginning of the leg, other times it is taken from the end of the leg and other times it is an average of the leg's initial and ending magnetic courses.

I would calculate that leg in two segments.  From GIJ to BENJO flying a course of 082 magnetic (50 NM), thence from BENJO to CRL on a magnetic course 087 (79 NM).

In addition, the magnetic variation is only applicable to hand plotting an arbitrary course using the map's orientation as a reference; IFR charts list true magnetic courses on their airways for ease of reference.

After that, you just need the winds aloft and you're off to the races!


Am I required to report an incident that isn't specifically mentioned in 49 CFR 830? I have read an understand NTSB Part 830, and know that IMMEDIATE notification to the NTSB is required for aircraft accidents and the listed serious incidents. My question is, is there a requirement to notify the NTSB or FAA of an incident that is not listed in part 830? This is not a question about accident reporting, but specifically incident reporting for incidents that are not listed in the regulation.
Possible scenario: While landing at an uncontrolled field, the airplane loses directional control and departs the runway into the grass and the airplane did not receive substantial damage nor was there a serious injury or death.

There are a couple of part 91 regulations that require 'general' incident reporting, but only if the FAA or ATC requests it.
14 CFR 91.3(c) says that if a pilot exercised emergency authority to deviate from part 91 rules then the FAA can ask for a report:

(b) In an in-flight emergency requiring immediate action, the pilot in
command may deviate from any rule of this part to the extent required
to meet that emergency.
(c) Each pilot in command who deviates from a rule under paragraph (b)
of this section shall, upon the request of the Administrator, send a
written report of that deviation to the Administrator.

91.123(d) says that ATC can ask for a report if they gave a pilot emergency priority, even if the pilot didn't deviate from any rules:

(d) Each pilot in command who (though not deviating from a rule of
this subpart) is given priority by ATC in an emergency, shall submit a
detailed report of that emergency within 48 hours to the manager of
that ATC facility, if requested by ATC.

There are also regulations for charters (135.415) and airlines (121.703) that have a long list of "service difficulties" that must be reported, including in-flight fires, brake failures and others. And there are likely non-FAA regulations on things like HAZMAT incidents.


Does the parking brake provide additional deceleration in an abnormal situation? During a rejected takeoff at a speed > V1, you obviously try to stop with all available means since a runway overrun is a very undesirable result. In this case, could using the parking brake in addition to the normal brakes and reverse thrust help slow down the aircraft faster?

I know that the parking brake can be used to slow down the aircraft, e.g. in the “no breaks available” memory item on an A320 but does it help when the normal brakes are available?

This is probably aircraft dependant, but I can give some examples for the airplanes that I have flown and will be generally applicable to transport category aircraft.  Understand that it won't cover every airplane as an absolute rule though.

In general, these types of airplanes have an antiskid system which keeps the wheels from locking up during heavy braking.  If they were to lock completely up, the tires would likely blow, greatly decreasing deceleration and making it more likely to run off the runway (either at the end or off a side).

Parking brakes often have multiple settings because of this.  One setting will be one which can be used when the normal brakes have failed, and have a relatively low brake pressure / stopping capability compared to the normal brakes in order to protect the tires.  Using this setting will stop the airplane eventually, but you are better off with the normal brakes which have a higher brake pressure with antiskid, and better deceleration.

Another setting would have a much higher pressure, intended to keep the wheels from turning (while it is parked), and this would be undesirable while attempting an abort.

In the end, I will say what I usually say:  Follow the guidance in the AFM.  If it says to use the emergency brake when you abort, then do it.  Most likely it will not (because of the above reasons), and you should not do it.  If you take it upon yourself to go against their guidance, you become a test pilot and are either trying something that hasn't been done before, or worse yet, something that has been tried and has had an undesirable result.


What are good resources on causes of private aircraft crashes? I'm working on getting my PPL, and I would like to read more about the specific causes of small private aircraft (single or twin prop, primarily) crashing, especially those that were caused by pilot error. Are there any good books or other resources on this matter? A decent amount of searching hasn't turned up much -- it seems like the data from private charter jets is often combined with that of the aircraft I'm interested in.

The AOPA's Air Safety Institute has quite a few resources that I like to review from time to time, including some great videos with commentary on exceptional cases.

AOPA ASI Accident Analysis Page
AOPA Accident Case Studies
AOPA Real Pilot Stories

I do exactly what you are doing, during training and still after, but I'd like to also say that you shouldn't narrow yourself to GA crashes, a lot of what happens commercially can be applied to GA, and usually with commercial accidents there is a lot more data and analysis available to work with. In that regard, I like to watch shows on Youtube like "Air Crash Investigation", or on TV like "Why Planes Crash" (some available on Youtube)

AOPA also has a lot of resources to view NTSB reports on individual crashes where you can search by certain criteria like aircraft type, states, type of flight, or even some specific keywords like "Vacuum Failure".

Just don't limit yourself to looking at things like "Pilot Error", pilot error is a broad category of crashes that is usually used to describe the pilot doing something wrong in the air, but a lot of crashes are "pilot error" in that the pilot could have broke the accident chain much earlier in the flight. Read as many as you can, regardless of the cause. For example an accident where the aircraft breaks up in flight may not be attributed to pilot error, but its good to know what lead to the break up and what could have been prevented.


What makes snow on the wings during take off so dangerous? What is the cause of the widely known danger of snow on the wings of the airliner? Why does it require deicing before taking off?

I cannot believe it just makes the plane too heavy, and it is not obvious if it could alter the wing shape for this to be a problem. Control surfaces may not move as commanded? Possible shape and balance differences between left and right sides when that snow starts leaving the wing?

it is not obvious if it could alter the wing shape for this to be a problem

It may not be obvious but it is so.

Plain old snow will just blow off as soon as the plane picks up speed, but if the wing was above freezing when the snow first fell on it, the snow will probably conceal a layer of rough ice, which will not blow away.

Anything adhering to the wing surface will change the lift force. According to this article even a thin coating of ice can disrupt an airfoil's boundary layer airflow, causing a premature aerodynamic stall and dramatically increased functional drag.


Why do different manufacturers recommend different throttle settings at startup? I was wondering why different engine manufactures recommend different throttle openings before engine start? On many Pipers 1/4 Inch is recommended while the Cessna 172N recommends 1/8 Inch and the Cessna 172S again recommends 1/4 Inch.
Why do we open the throttle before starting the engine? What difference does it make opening the throttle more or less, has it to do with the fact that it isn't good practice to have high engine power when the engine is still cold and oil pressure is low? And why should we open the throttle differently when the engine is flooded or we start the engine when it is still hot?

It's just a ballpark value that someone decided on during testing, that provides enough air to the engine to let it start and run with a rich primed mixture, without causing too much initial RPM.  A quarter inch here, and eighth inch there, it's all good as long as it doesn't cause the engine to burst into life at high power, and nobody expects you to sit with a measuring stick to get it exactly right.
It's not a good idea to start an engine with a very high throttle setting, because high rpm before there is sufficient oil flow = bad in the long run.  Crank and rod bearings need to be fully pressurized before any significant load is put on them. Cam followers need to be well coated in oil before they spin at more than minimum speed (especially with Lycomings).
Most engine wear happens in the first 15 seconds of starting, when the oil flow is inadequate and bearings, piston rings, cam lobes and gears etc are running on only a residual oil film.  Once a plain bearing is fully pressurized with oil, there is no metal to metal contact and the life of the bearing, in theory, is infinite.  If you ran a 2000 hour TBO engine with just one start and let it go without ever shutting down and just kept it supplied with fuel and oil 24/7, it would run far far beyond its normal TBO (although it might need cylinders at some point as valves wear out).
My personal practice is the use the absolute minimum throttle opening that will let the engine start, and let the engine tick over at minimum speed until I see normal oil pressure, before I go to a warm-up RPM. When an engine is warm, that usually allows starting with the throttle completely closed. Oil gets to where it needs to pretty fast; it's just that initial 10-15 seconds that's critical.


How does an altimeter deal with the non-linear pressure gradient? Altimeters work via an aneroid barometer to sense the atmospheric pressure. If I climb from 2000ft to 4000ft, the altimeter senses that the pressure has reduced by, let's say, 70hpa, and is calibrated to know that 70hpa = 2000ft.

But the pressure gradient (or rate of change of pressure) reduces with altitude. A climb from FL240 to FL260 might result in a pressure reduction of only 30hpa. Yet it still knows that the aircraft climbed 2000ft. How does the altimeter do this?

It uses a model called The International Standard Atmosphere (ISA) - so may be inaccurate if you don't have one of those to fly through :-)


What does the autopilot do if activated in a stall condition? I was thinking about Air France 447 recently and had a wonder:
What would happen if the pilots had re-engaged the autopilot and stopped all stick input? (If that's even possible in a stall condition). I know this has since changed, there is the MCAS system now, which will force a stall recovery. But in an older aircraft, like the A330 - 203, what would happen?

In the AF447 accident, the autopilot disconnected because of inconsistent airspeed:

Temporary inconsistency between the airspeed measurements, likely following
the obstruction of the Pitot probes by ice crystals that, in particular, caused the
autopilot disconnection and the reconfiguration to alternate law;

(BEA - Final Report)
As long as the airspeed remains inconsistent, it is not possible to re-engage the autopilot:

Two ADR outputs are erroneous but different and the remaining ADR
is correct, or if all three ADR outputs are erroneous but different. The
AP and A/THR will disconnect. If the disagreement lasts for more than 10
seconds, the PRIM triggers the NAV ADR DISAGREE ECAM caution.
Flight controls revert to ALTN 2 law. The SPD LIM flag is displayed on
both PFDs, however VLS and VSW are not displayed. This condition is
latched until a PRIM reset is performed on ground without any hydraulic
pressure. However, if the disagreement was transient, the AP and A/THR
can be re-engaged when the NAV ADR DISAGREE message has
disappeared.

(Airbus A330 FCTM - Non-normal operations - Unreliable Airspeed Indications, emphasis mine)
It is not known if the crew attempted to re-engage the AP with the pushbuttons on the FCU because this is not recorded by the FDR:

It is also impossible to see whether there have been any attempts to re-engage the autopilot.

(BEA - Final Report)
The BEA did a study of similar incidents and found that the AP was re-engaged in some of these:

The BEA has studied thirteen unreliable indicated airspeed events involving the
temporary loss of this reading, or other anomalies, for which it had access to crew
reports, recorded parameters and PFR. [...]

The aircraft’s autopilot disconnected in all cases, with no intervention from
the crew;
[...]
In seven cases, an autopilot was re-engaged during the event. In two of these,
the re-engagement occurred even though two speeds were consistent with each
other, but erroneous;

(BEA - Final Report)
So it is possible to re-engage the AP after it automatically disconnects due to unreliable airspeed, but these events were not fully developed stalls. Your question seems to ask about the situation later on where the incorrect manual inputs had already resulted in a stall. In these cases, re-engagement of the AP would likely not be possible due to the engagement conditions:

AP Engagement
AP can be engaged when:

Aircraft speed is within VLS and VMAX.
Aircraft pitch angle does not exceed 10° nose down or 22° nose up.
Bank angle is less than 40°
[...]

(Airbus A330 FCOM - Auto Flight - Flight Guidance - Autopilot)
In a stall the speed or pitch limits are likely exceeded preventing autopilot re-engagement. This is a part of the FDR recording from AF447 (you can see that pitch never exceeded the 22°, but the airspeed went down to 38 kt towards then end of the flight while the F/O pitch command was at the nose-up limit):

(BEA - Final Report)
If the autopilot would re-engage successfully, it will do what it is programmed to do: follow the flight director inputs, which depend on the selected mode on the FCU (therefore just turning on the AP is not enough, one also needs to select appropriate modes on the FCU).


Why are there two IRS switches on the 737NG? I've noticed in some videos,that there are two IRS switches on the 737NG. Why is that so and what is the primary purpose of IRS? Also, what is the alignment of the IRS mean?

Inertial Reference System is a solid state set of 3 ring gyros which navigate using dead reckoning.  The system measures accelerations in  and rotation around each of the 3 axis so can calculate where it is by adding how much it has moved to the initial position.

A simple example:
The aircraft is stationary pointing North.  Over a 10 minute period, it measures the accelerations in the X and Y axis and calculates that is has moved +100 kms in the X axis (i.e. North) and +100 kms in the Y axis (i.e. West).  By simple trigonometry, we can calculate that the aircraft is approximately 141.4 kms on a bearing of 45 degrees from it's initial position.

The gyros must be aligned with the aircraft frame of reference when it is stationary.  This is the "alignment" process and generally must be completed before the aircraft moves.  It may also take inputs of the current position from a manual keyboard or from some other system, e.g. GPS.

More modern IRS fits can align when the aircraft is moving, taking an updated position from GPS.

There are 2 systems on the 737, simply for redundancy.

This slide show gives a good overview.


Has this type of "gyrocompass" ever been used in an aircraft? One type of instrument commonly referred to as a "gyrocompass" is commonly used in ships.  It detects true north based on gyroscopic precession, and is not slaved to any magnetic compass or any magnetic sensor of any kind, nor is it necessary that the instrument be frequently manually corrected by reference to a magnetic compass.  Has this instrument ever been used in aircraft, and if so, what are some examples?

The intent of the question is to ask about specifically about instruments that benefit from an intrinsic north-finding property related to the earth's rotation, including cases where this property is used to correct for various errors that would otherwise eventually cause the system to drift out of its initial orientation.

I think the answer is "no and yes".  Bear with me...  That sort of device as a stand alone heading sensor has never been used in an aircraft and if you parse the Wikipedia article carefully it becomes apparent why, under the paragraph titled "Errors".

  A gyrocompass is subject to certain errors. These include steaming error, where rapid changes in course, speed and latitude cause deviation before the gyro can adjust itself.[12] On most modern ships the GPS or other navigational aids feed data to the gyrocompass allowing a small computer to apply a correction. Alternatively a design based on a strapdown architecture (including a triad of fibre optic gyroscopes, ring laser gyroscopes or hemispherical resonator gyroscopes and a triad of accelerometers) will eliminate these errors, as they do not depend upon mechanical parts to determinate rate of rotation.[13]

To work it requires a very slow moving and stable platform (like a ship). Anything approaching rapid motion, even by ship standards, let alone by aircraft standards, requires external help of some kind.

This rules out aircraft, and small boats for that matter I expect.

"Gyrocompass" in aviation has always referred to a directional gyro that is continuously slaved to an external magnetic north sensor.  The traditional system has some form of directional gyro, either right in the instrument panel or built into an Attitude/Heading Reference System (AHRS) unit that drives the cockpit heading indication, with the actual magnetic field sensor in a remote location, usually out at the wing tip, called a Flux Valve, that provides a continuous magnetic north reference, to which the gyro is aligned.

When not slaved to the Flux Valve, an aircraft gyrocompass becomes just a directional gyro, which must be set manually and corrected for precession manually (on an AHRS system you will have a MAG/DG switch that allows you to select slaved or unslaved indications - in the high arctic where compass indications are useless, you have to operate in DG mode).

Now, I said "stand alone" for a reason. Inertial Reference Systems (or Inertial Navigation) used for aircraft navigation do use this phenomenon for their initialization alignment process.  IRS initialization/alignment is done normally on the ground with the aircraft stationary, but can also be done in flight if heading is held steady during the alignment. The system is told where the aircraft is geographically, by entering lat/long or by GPS/FMS input if equipped, and the IRS senses precession from the earth's rotation to figure out what direction the airplane is pointed relative to true north (because it can sense the west-east axis of the earth's movement and knows the airplane longitudinal axis relative to that).  This is how IRS systems get their directional starting point, from which future indications are derived from inertial changes from the starting point.  If inertial errors build up in the system (you get left right IRS position comparator errors), the system has to be aligned again (which is why there is usually a procedure to do an "IRS Align" in flight where you fly a constant heading, speed and altitude for several minutes while the IRS does its thing).

So the answer is, yes, but limited to IRS systems when starting up, and no as a stand-alone heading device.


On an A320, will the aircraft compensate for constant pilot rudder input? As I understand from answers to the question What does rudder input control in normal law in an A320?:

the rudder deflection is the result of the sum of pedals input and plane's FBW command
in normal law, the FBW tries to fly with zero slip angle

This seems reasonable so that any asymmetry is automatically compensate.
But what happen if this asymmetry is due to constant non neutral pedals'input?

Will the aircraft compensate for constant pilot rudder input? No.
It seems you're asking if a pilot can deliberately sideslip an A320 while in normal law (Gimli Glider style).
The answer is yes. The normal law won't fight back.
The question has been asked years ago on pprune.org, where one person replied:

Great question....one that is misunderstood by many....too many.
Please refer to FCOM 3.04.27 P4, FCTM NO-160 P 3/12 (24 JUN 09), and Airbus Flight Operations Briefing Note "Landing Techniques....Crosswind Landings" (April of 2006).

The user is referring to the pilot being able to indeed induce it during a crosswind landing before touchdown (unlike pitch, there is no flare mode for roll/yaw).
But if you're like me, you'd want more proof. Sadly the proof comes from a 2012 incident where the captain was incapacitated and involuntarily pushed on the rudder pedal:

(Final report)
The relevant text from the final report reads:

Approximately seven seconds after the captain’s last attempt to communicate, autopilot 1 was disengaged by the co-pilot, at this time the travel of the captain’s right rudder pedal reached approximately 13 degrees, and the Aircraft started to sideslip. The co-pilot disengaged autopilot 1 when he decided to take over control after realizing that the Aircraft was side-slipping. However, after the autopilot disengagement, the captain’s right pedal was still being subject to pressure continuously while it maintained a position of 14±1 degrees for another 18 seconds.
Autopilot 2 was engaged by the co-pilot in order to reduce the workload, but after seven seconds, the co-pilot disengaged it due to, most probably, noticing the continuous input of the captain’s right rudder pedal, which put the Aircraft into a 10 degree sideslip, and to lateral acceleration that reached approximately 0.26 g.
After the 18 second period of constant pressure on the right rudder pedal, the rudder input started to decrease and the pedal returned to the neutral position within 11 seconds. During the 29 seconds from the captain's full coma until the pedals returned to the neutral position, the co-pilot was making continuous attempts to recover the Aircraft to straight and level flight manually.

Addendum: Note that the A320 normal law doesn't aim for zero sideslip, rather coordinated turns, i.e., when a roll is commanded with no pedal input. Also a pre-programmed partial rudder input is made when an engine fails, but the remaining required input is left to the pilot (to maintain the pilot's instinctive reaction). And finally yaw damping acts on the yaw-rate (oscillation) due to Dutch roll. None of which would (nor should) act against a pedal action (as the incident and crosswind landing technique demonstrate).
In yaw damping and turn coordination, the one-way artificial feel cancels any feedback on the pedals (and adds feedback when yaw trim is input), but a pedal action will always work the opposite way on the rudder.


Can pilots smoke in the cockpit of an airliner? An answer on travel.se suggests that some pilots are smoking on long-distance passenger flights.

Can passenger airliner pilots smoke if both the captain and first officer agree it’s ok? If I recall, smoking is only prohibited on flights that require cabin crew as a crew health issue (sidestream smoke) and not as flight safety issue. Given that cabin crew are not on the flight deck, is there anything that prevents a pilot on a larger airline from lighting up?

For the purposes of the question, let’s consider flights originating in  USA, EU, UAE, and China as the four biggest country/areas.

All of the most significant countries prohibit smoking on airline flights, either through national, industry, or airline regulations. This applies to crew through different regulations, but as strictly as to the passengers.

Pilots can and sometimes do smoke in the cockpits of business jets. These can be as large as airliners (see BBJ), but usually aren't.


What is the bend in the tip of the blade of the new Black Hawk? The newer Black Hawks have this angle added to the end of their rotor blades.

What is it for? How does it increase or decrease performance?
Could this be used on airplane propellers?

(verticalmag.com)

It is blade sweep, used to delay compressibility effects at the rotor blade tip. From Leishman:

  The blade tips encounter the highest dynamic pressure and highest Mach numbers and strong trailed tip vortices are produced here.

Blade tip designs can get quite funky, but the UH-60 tip has a relatively simple straight sweep. Again from Leishman:

  The amount of sweep is usually kept low enough (< 20º) so that there are no inertial couplings introduced into the blade dynamics by an aft centre of gravity or by aerodynamic couplings caused by a more rearward centre of pressure. A constant sweep angle offers simplicity in design and construction, but may result in higher than desirable aerodynamic torsional couplings because of the rearward location of the local centre of lift.

So by delaying compressibility effects in the forward going blade, the helicopter can fly at a higher maximum speed.

  Could this be used on airplane propellers?

It could, and it is being used. This company offers swept blade propellers as an upgrade for the King Air series. They look a bit different because the sweepback for propellers is best started at quarter chord.

And the A400 uses swept blade propellers as well.

The simple sweepback on the helicopter rotor is a trade-off between aerodynamic efficiency and production costs. The same trade-off allows for more complicated propeller shapes, such as in the Wiki article for scimitar propellers.


Legal requirements for electronic flight bags like Foreflight or SkyDemon I’m wondering what the legal requirements to use EFBs like ForeFlight or Skydemon or similar for primary flight planning and navigation. If I remember correctly, I once heard about requirements on battery percentage, backup device, external battery or similar.

In particular, I’m interested in the situation in Germany, but I’m happy to hear about differences to other countries (e.g. FAA vs. EASA) as well. I’d be happy about hints on where to find regulations like these as well.

you actually have two questions here

  ...for primary flight planning

EFB's with up to date charts are legal for planning and reference as covered in this question.

Many EFB's (well at least foreflight that I know of) here in the US allow you to file flight plans, and receive briefs from a weather briefer right in the system.

  ...and navigation

EFB's are legal for navigation as you would use a map but they are not legal replacements for GPS/AHARS units despite the features they have. Simply put they are not TSO'ed and not legal navigation instruments.

This is also spelled out in the regs directly

  The EFB system does not replace any system or equipment (e.g.
  navigation, communication, or surveillance system) that is required by
  14 CFR part 91.


How many Inertial Reference Systems are on a commercial aircraft? Nowadays all new airplanes have GPS on board so the use of IRS may lose  importance, still they must be fitted. How many of them are usually on a commercial aircraft? Does the regulation impose the number?

The answer is at least two. Although depending on how you view the system, either one, two or three can be a valid answer.

In the past, each IRS (Inertial Reference System) is itself a unit, and manufacturers would put multiple number of this unit in the cockpit. For example, the Boeing 737 has IRS L and IRS R. The pilots can power each unit on or off individually; they can also choose which unit goes to which display (captain side or copilot side). So in the Boeing 737, the answer to your question would be two.

Fast forward to the Boeing 777, the pilots only have one such unit: the ADIRU, or Air Data Inertial Reference Unit. The ADIRU by itself is a fault tolerance unit - within this unit, there are multiple gyroscopes and accelerometers. In the past, when multiple redundant units are provided to the pilots, there were instances where the pilots had trouble identifying the malfunctioning unit or switched to the wrong unit, and the plane crashed. Now there is only one unit, and the redundancy mechanism is auto-managed. So to answer your question for the Boeing 777, the answer could be either one or three.

It should be noted that even GPS has redundancy: there are usually two receivers: GPS L and GPS R. On newer airliners, all the data - GPS L, GPS R, ADIRU, VOR/DME etc. are combined to form a navigation system. Therefore one can say, "In the past there were 2 IRS, which consisted of gyros, on airliners. Nowadays we still have gyros, but we don't call them IRS because they form an integrated system with other elements".


Are there any pressurized piston-engine aircraft? Are there any pressurized piston engine-powered aircraft? Or does pressurization require a turboprop or jet?

The first pressurized aircraft were piston powered, beginning as early as 1921 with a modified Airco DH.9A containing a pressurized enclosure for the pilot.  Throughout the 20s and 30s, pressurization systems developed in reciprocating powered aircraft with benchmarks like the Lockheed XC-35 being the first pressurized aircraft using bleed air from its super chargers to pressurize the cabin and the Boeing 307, the first pressurized airliner.  World War II saw plenty of pressurized pistons like versions of the BF-109 and the Ju-86, as well as the Boeing B-29.

Postwar airliners were also pressurized.  The Boeing 377, the Douglas DC-6 and the Lockheed Constellation were all good examples of this.  With the introduction of jets, these quietly faded into obscurity.

There are a few pressurized piston single and twins in operation today, though manufacturers did not make very many.

Probably the most successful pressurized single is the Piper PA-46 Malibu series introduced in the 1980s and still in production today, in both the form of the reciprocating PA-46-350 Mirage and the turbine powered PA-46-500 and -600 Meridian.

In the late 70s and early 80s a number of manufacturers attempted to enter the pressurized entry cabin class single engine market.  Cessna offered a Pressurized version of the C-210 Turbo Centurion called the P210 which is no longer produced but still popular with GA pilots today.  Mooney, after finding marginal success with its pressurized M22 Mustang from the 1960s, decided to produce a pressurized six seat cabin class airplane called the Mooney 301.  It was stillborn due to financial pressures from Mooney's new owners but the best technology from it was cannibalized in a ill-fated partnership with Aerospatiale (now Daher Socata) in Tarbes France to produce a single engine turbine airplane which eventually became the TBM-700/-850/-9XX (TBM stands for Tarbes Mooney).

Even a few homebuilt piston singles have been pressurized.  Lancair's IV-P, ES-P, and piston versions of their Evolution are all pressurized and capable of nearly 300 KTAS at FL250.

More piston twins have been pressurized as well.  Cessna produced a pressurized version of the C-337 Skymaster called the P337G, as well as the 340, 414 and 421.  Piper produced the PA-31 Navajo.  Beech produced the BE-60 Duke as well as a variant of the Queen Air called the B88. Rockwell produced the Aero Commander series.