Is deicing fluid harmful to the environment? How harmful is the fluid applied on aircraft to the environment? Is there any way to collect this waste fluid to minimize this, if in fact it is harmful?

The main component of deicing fluid is either Ethylene Glycol (EG, toxic) or Propylene Glycol (PG, non-toxic) (source) and depending on the category applied different amounts are used annually.

There have been studies of the environmental impact of deicing fluid, which basically states:

In water, EG is not persistent and biodegrades aerobically and anerobically.
In air, EG is not readily volatile and its atmospheric half-life is approximately 1 day
In soil EG is also not persistent and biodegrades anerobically in about 1 day
EG is disposed of and treated at standard wastewater plants

(I think the above comments also apply to PG, but somebody will have to confirm that since I can't find anything that mentions it).

PG is non-toxic and is used in quite a few products that you use every day, from pharmaceuticals to food additives and moisturizers. I can't confirm but one of the linked articles says that most of the DI fluid used in the US is PG based, which I would believe, but can't source.

And from the article quoting an EPA Report 821-R-00-0016, January 2000, Revised August 2000,

  Although EPA does not use such a system, the
  U.S. Fish and Wildlife Service Classification
  System for Acute Exposures defines ‘relatively
  harmless’ as any chemical with an LC50 above
  1,000 mg/L. The test results … indicate that
  ethylene glycol and propylene glycol may be
  classified as ‘relatively harmless,’as defined by
  the U.S. Fish and Wildlife Service.

There is also one manufacturer using 1,3-propanediol which is a by-product of corn fermentation and should be relatively minor as far as environmental impact.

There is also considerable movement in airports to "go green" and recover used deicing fluid, especially considering that a larger aircraft can take more than 1000 gallons of diluted deicing solution at the rate of up to $12/gallon, quite a bit of which runs off the aircraft and onto the ground. In fact, the EPA has mandated that new airports in cold climates recover 60% of DI fluid.

Edit

It may be important to note that the point of DI fluid is to keep the snow/ice off the aircraft until it leaves the ground, not assist in flight into known ice. Depending on the fluid applied, they usually only stay on until the aircraft reaches about 100kts. This means that most of the applied DI fluid is going to end up in the airports wastewater system because most will run off the aircraft on the ramp/apron, not spread around the countryside as the aircraft flies around.


Why is "NoPT" indicated on this KYKM approach? For LOC-DME approach (back course) at Yakima Air Terminal (KYKM), NoPT was mentioned at different locations on this 2008 plate:

Click for full plate. Source.

However there is no procedure turn at all. Why is NoPT mentioned?

FAA_H_8083-15B Instrument Flying Handbook 2012

Procedure turn. A maneuver prescribed when it is necessary to reverse direction to establish an aircraft on the intermediate approach segment or  final approach course.

This particular approach doesn’t have a course reversal—the DME arc takes care of the course change from the YABLU IAF and the DATVE IAF. (Cut off on your map.) BABRE is an intermediate fix, and again needs no reversal.

So as you mentioned, there is no reason to state NoPT.

The version of the chart you used in your post is out of date. The current chart doesn’t mention NoPT, probably because there is no reason to. I’m guessing that mentioning it on your version is a mistake that they have since corrected or they are conforming to newer standards for chart making.


Can an aerodrome in class G airspace be controlled? Can an aerodrome be controlled, even if the only associated airspace is classified G?

E.g. can such an aerodrome have a control tower with the authority to give takeoff and landing clearances and taxi instructions?

I know the opposite is possible (uncontrolled aerodromes in class D airspace for example).

I am not asking about AFIS aerodromes, since AFIS is not an air traffic control service.

Please provide examples and/or references to ICAO SARPs or national regulations.

An airport in class G airspace can have an operating control tower. This is a case of a towered airport in uncontrolled airspace. The airspace is uncontrolled but tower communication must be established within a certain distance and for use of the airports runways.

There are applicable regulations that address this situation. 14 CFR §91.126 (d) requires pilots to establish and maintain communication with a Class G towered airport before entering a 4 NM radius below 2500 AGL.

As of today, Lake City, Florida (KLCQ) is an example of such an airport, although that will change at some point in the future.


Do you pay to Touch-and-Go? I understand you pay to land at an airfield, but do you pay to Touch-and-Go?

Pilots will often practice many Touch-and-Go's at an airfield, are you billed for each one (assuming you pay something to use the airfield's resources for the Touch-and-Go procedure).

How are you charged if you don't do a full-stop at the field (practicing at another airfield different from your home base)?

It varies.  Some airports charge by landing, others by operation (a series of landings if training).  Some charge through the FBO, who may waive the fee with fuel purchase.  Expect that multiple landings at BOS or JFK will result in multiple fees, often billed to the registered owner.  It was a while ago, but I did a series (about 12) of landings at BOS one night, and the owner/operator paid 25 dollars each. Someone told me recently that the fee was more like $65 now for a Cessna P210.

To be clear, call the airport and ask them, or check their web page, which may have their charges and rules on it.  And/or check with an FBO or two at the field.


Do I have to notify ATC if I go-around when I was cleared for a touch and go? If I was cleared for a touch and go and go-around on short final or just before touchdown, do I have to notify ATC?

I still would have made a takeoff after the touchdown during a touch and go, so it's basically the same when I start the climb a few seconds earlier isn't it?

From the Instrument Procedures Handbook, page 4-41 (as part of the Missed Approach section), there is a quote about what to do when you need to go around when operating beyond the missed approach point:

  In the event a balked (rejected) landing occurs at a position other
  than the published missed approach point, the pilot should contact ATC
  as soon as possible to obtain an amended clearance.

I have seen several other references in FAA documents which say to "contact ATC as soon as practical" in similar situations, but nothing which specifically says to do it any time that a go around is initiated by the pilot (i.e. under VFR).

That being said, if you have received a specific clearance (for a touch and go), and decide that you prefer to do something else (low approach/go-around), you should always receive an amended clearance first.  If you know ahead of time, your best option is probably to request the "option", in which case you have a clearance to do either one.

On the other hand, if the reason for the go-around is due to a safety issue then execute the go-around immediately when needed, and follow the above guidance to contact ATC as soon as practical if they don't call you first.

I was taught by my flight instructor to always report it, and the tower certainly needs to know about it in order to provide proper separation with other aircraft operating in the area.  If nothing else, it is a "best practice" to ensure that the person in the tower doesn't get distracted and not notice that you didn't land.


What improvement was made in Su-35 over Su-30? What improvement was made in Su-35 over Su-30?

The Su-30 is an modifications of the SU-27UB
The Su-35 is an Su-27 shaped aircraft with many new parts from the Su-34 (T-10BM)
in detail
Radar N035 Irbis-E PESA
Rear-looking self-defense radar
new fly-by-wire flight-control system
new fully-glass cockpit
Electronic-warfare self-defense system L175M Khibiny-M
Engine AL-37FU/ 117S
larger Air Intakes, no canards, reduced-area empennage

Su-35 has been also called early export versions of the Su-27
and to make more confusion, the production factories (Irkut / Amur) does not name their product Su-35

Please take a look at   http://www.sukhoi.org/eng/planes/military/Su-35/
and   https://defence.pk/pdf/threads/su-30mki-vs-su-35s.222304/


Why are Western helicopters more expensive, yet smaller in size, but Russian helicopters are way less expensive, and larger in size? So, I was looking around for prices of the Bell 412, Blackhawk and Mil Mi 8/17 prices, and the Bell 412, despite being a lot smaller than the Mi8, was US$2mil more than the Mi8.

It's just market.
Like most markets, it's not even entirely rational. In the end, people may just have preferences. It commonly happens that a car X is cheaper than Y (and/or depreciates more), despite being better on every objective measure as a vehicle. But on the Y's side may be long-term reputation, familiarity, etc.
Still, there are many perfectly rational reasons for such disparity (lower cost of Russian aircraft), particularly in the West.

Service cost and, even more importantly, its availability. Russia is not particularly renown for its after-sales service, even within the country. A grounded aircraft is a big money drain.
Likewise, availability and cost of pilots for such less common aircraft. This includes training, licensing them etc.
Typically higher fuel consumption per unit payload (for the same generation of aircraft).
Typically smaller service intervals and shorter overall lifetime. This is partly due to military origin of most Soviet/Russian helicopters.
Depreciation and later sale prospects. This is somewhat a vicious circle, but it's an important factor affecting purchasing decision.


In what way are the airfoils used for a propeller different from the ones used in turbofan engine? Airfoils are used in the blades of a propeller as well as the blades of the fan, axial compressor and turbine in a turbofan engine. Thus, the airfoils used in above two applications have different purposes. In propeller, the lift from the airfoil is used for generating thrust. Whereas, in a turbofan engine, airfoils are used for adding and extracting work from the flow in the compressor and turbine sections respectively. Therefore, my question is what are the characteristics of the airfoils employed in both propeller and turbofan engine, and how they vary from each other. Also, how different is the blade section of a fan with respect to the ones in axial compressor and turbine.

The angle of attack range of a propeller airfoil is larger than that of a turbofan. Therefore, the turbofan can get away with a thinner airfoil and much more camber. Also, the aspect ratio (ratio between length and chord) of a propeller blade is much higher, so the airfoil needs to be thicker to allow the blade root to carry the radial loads and to produce less torsion so the propeller blade does not twist too much under load. Were the turbofan blade as thick, the higher solidity of a typical turbofan would mean that the fan blades would block most of the flow path.


How do I submit a NOTAM? I (a hypothetical person) am involved in an activity like laser light shows, model rocket launches, fireworks displays, or construction which I think might be important to pilots. How can I submit this information to the FAA so that they can issue a NOTAM?

When I have had to file NOTAMs for skydiving demonstration jumps, I just called AFSS (1-877-4-US-NTMS) and asked to file.  The folks at Lockheed are way more helpful than the Feds used to be and will walk you through the process, but it is still good to have your information together before you call.  At a minimum you need a description of your activity, altitudes in MSL, times in zulu, and a location.  Location should be in reference to an aiport or nav aid ("Within one nautical mile of the BFE airport", or "27nm from the BADGER VOR on the 340 radial, for a radius of 2 nm").  If the activity requires authorization, you will also need to have that squared away before calling.


For the elliptical wing, which property is actually elliptically distributed? Elliptical wings are sometimes used:

One of the 50 Spitfire still flying in the World. Source
I read it's because this shape allows a perfect distribution of aerodynamic forces. But actually:

What is actually elliptical in the elliptical wing?
What is regularly distributed: Is it lift? or drag? or something else?

It is both the planform and the circulation distribution. Note that circulation is not lift coefficient but bound vortex intensity. You can interpret it as local lift coefficient times local chord.

On the untwisted elliptical wing the local lift coefficient is constant over span, and changes in angle of attack over the linear range will change the lift coefficient equally everywhere. This, when combined with the elliptical chord distribution over span, means that the circulation distribution will stay elliptical over the linear angle of attack range. This is the special characteristic of an elliptical wing: While any wing can have an elliptical circulation distribution at one angle of attack (given the right twist distribution), the elliptical wing will keep that elliptical circulation distribution over the whole operating range.

With an elliptic circulation distribution comes also a constant induced angle of attack and downwash angle over span. I guess this is expressed by some authors with the term "regular".

However, only the aerodynamicists will see that as an advantage. Both weight and stall characteristics of elliptical wings are less than optimum; the low induced drag coefficient is bought with higher structural mass and, consequently, lift. A more triangular circulation distribution will yield the lowest wing weight and overall drag for a given non-lifting mass (that is, all mass that is not involved in lift generation, especially the payload). Note that for such a triangular distribution drag will be highest near the center.

When people talk about elliptical lift distribution, they mean lift per span. I prefer to use the more correct term circulation, since lift is a force as in pressure times area and can only be produced by a whole wing or at least wing section, not one spanwise station.


Based on what concept/strategy is a new aircraft ICAO code assigned? I refer to the official ICAO database.

BOEING  747-8 BBJ   B748    LandPlane   Jet 4   H
BOEING  BBJ (747-8) B748    LandPlane   Jet 4   H

I fail to understand when ICAO assigns a new code, and when not. As an example, I do not see the reason why there are 2 entries (in the database) like the ones above.

In other cases there are no ICAO codes at all, like for the A330-800/900 NEO. So I wonder what process does ICAO use to create a new code. Any idea?

The downloadable comprehensive PDF (icao.int) only has one listing for the 747-8.

Compared to the website search function:

My speculation is that the website search accommodates someone searching for "BBJ" in different ways (why, I don't know), or the database needs cleaning up. As you can see, two of the three are the same. And judging by the actual designator, they are all the same.

As for the rules:

They are to be found in ICAO DOC 8643, Aircraft Type Designators; or FAA JO 7360.1B - Aircraft Type Designators. The FAA Job Order is 2 months old and also contains the full list.

The relevant part to this question:

  A different designator for an alternate or subtype version of the aircraft will only be allocated when there is a significant difference in performance for ATS or no shared designator can be assigned.

(Emphasis mine.)

That means the A320neo has significant performance change (A20N vs. A320). A plane like the Boeing 777-200 with three engine options doesn't need different designators. The A330neo is yet to fly, but A339 comes up on the website search. Nothing came up for the A330-800neo.

Related: What will the 737 MAX 7, 8, and 9 ICAO IDs be?

The full rules:

  2-2. How Designators are Formulated. The International Civil Aviation Organization (ICAO) has the role
  of creating standard aircraft type designators for aircraft that commonly request air traffic service. ICAO
  assigns an aircraft type designator using the following principles:

  a. Only one designator will be assigned per aircraft type.

  b. A designator will be derived from the manufacturer’s model number or name, or from a common
  military type.

  c. The designator will not be longer than four characters and will generally begin with a letter.

  d. An assigned designator will not be changed for license-built aircraft, when an aircraft model is sold to
  or manufactured by another company, when the manufacturer’s name changes, or when the aircraft type is
  derived or converted from another type.

  e. A different designator for an alternate or subtype version of the aircraft will only be allocated when
  there is a significant difference in performance for ATS or no shared designator can be assigned.

  f. “Homebuilt,” “amateur-built,” or “kit plane” aircraft that exist in operationally significant numbers will
  be assigned a designator; however, these aircraft will only be listed under the original designer or under the
  manufacturer that produces or produced the aircraft type in series.

  g. In general, an aircraft type designator will be assigned to all aircraft heavier than micro-/ultra-light. For
  the purpose of ICAO Document 8643:

    Micro-/ultra-light are those aircraft types with a maximum certified take-off weight of 1,000 pounds
    or less and a stall speed not greater than 35 knots.
    Micro-/ultra-light helicopters and gyrocopters are those helicopters or gyrocopters with a maximum
    certified take-off weight of 1,000 pounds.
    Micro-/ultra-light autonomous, optionally piloted, and remotely piloted aircraft are defined as
    having a maximum certified take-off weight of 330 pounds or less and a stall speed not greater than 35 knots.
    Micro-/ultra-light autonomous, optionally piloted, and remotely piloted helicopters are defined as
    having a maximum certified take-off weight of 330 pounds or less.

  h. Roman numerals used as part of aircraft model names or numbers will be replaced by Arabic numbers.


On the new A320s when we do a brake check there is no need to call pressure 0 why? Why do we have a give a pressure 0 call out when checking brakes while taxi on the old A320s but not in the newer A320s.?

I found an answer here: https://www.pprune.org/tech-log/456530-a320-brake-check.html

The complete fly by wire braking system apparently eliminates the check for residual pressure (check zero) of the older models, probably because the valve that determines which hydraulic pressure reaches the brakes is either no longer present or automatically tested anyway.

The new a320 also has a different PTU design which no longer barks...


Will talking about sleep problems with my doctor jeopardize my medical? I am asking this for someone I know who's up in years but still under 60, and is a fellow pilot.  He brought this question up:

"I am concerned that I might have some moderate sleep problems - doubtful it's narcolepsy, and I've driven (and flown) safely for years and the worst is feeling tired.  My thought is to check on blood levels and maybe EKG stuff etc..  Perhaps there is something that's actually detectable.  Perhaps there is medication that reduces the tiredness.  If I go to a doctor and bring these up, will it jeopardize my medical?"

Your thoughts?  Appreciate your feedback - my friend is not an internet person at all :)

In the US the HIPAA rules often provide you with confidentiality but there are several circumstances that allow your doctor to provide info without your consent and being a pilot qualifies. It allows them to, but only requires them to in situations where a crime might be involved, i.e. physical abuse.

The concern would probably not be that your doctor will tell the FAA (although they probably could if they were truly concerned), it would be that you would be required to tell your FAA examiner of any diagnosis. I believe it's a felony not to.

If it's sleep apnea he's concerned about (you said sleep problem, non-narcolepsy - I'm not a doctor so I'm just offering what i know about a very common sleep problem) then there are ways to get a special issuance medical certificate.

I'm not a pilot but a driver and I have to have a DOT medical card. The way sleep apnea is usually treated is by CPAP. For the DOT physical, If you are on CPAP you have to bring the machine to your physical so the examiner can check the data and verify that you have been using it (I think 75% of the time but don't quote me on that). I checked and the FAA has similar rules.

I agree with Pondlife that one's health should trump licensing concerns, and nobody should be flying if they are at risk of dozing off. But I definitely understand your friend's situation. I suspected I had apnea but I refused to go to a sleep study because I did not want the diagnosis. What if I couldn't deal with CPAP? My dad was on CPAP for 30 years but he rarely used it because it was too uncomfortable. Then I'd be forced to use it to keep my job.

Fortunately my situation resolved itself (I don't have apnea) but I understand why he's reticent to mention it to his doctor.


Does the NTSB provide CVR audio recordings alongside transcripts in accident reports? Reading the NTSB's accident report on US1549, there is a transcript of the CVR from page 149 onwards in the PDF (marked as page 130 on hardcopy).

Small clips of the ATC/crew communications exist, but I'm curious to know whether the NTSB also release the full audio recording, per the transcript provided? It's much longer than other clips I can find online.

Related: Can I get official recordings of ATC audio? (asks for FAA, not NTSB).

No. Federal law prohibits the NTSB from releasing any CVR recordings, and the NTSB notes that they are exempt from FOIA requests. The same law requires them to release a transcript, like the ones seen in accident reports, if the transcript is relevant to the accident or incident.

See 49 U.S.C. § 1114(c):

  (1) The Board may not disclose publicly any part of a cockpit voice or video recorder recording or transcript of oral communications by and between flight crew members and ground stations related to an accident or incident investigated by the Board. However, the Board shall make public any part of a transcript or any written depiction of visual information the Board decides is relevant to the accident or incident—

  (A) if the Board holds a public hearing on the accident or incident, at the time of the hearing; or

  (B) if the Board does not hold a public hearing, at the time a majority of the other factual reports on the accident or incident are placed in the public docket.


Is it possible to prevent plane accidents due to fuel explosion? We know that most of the plane accidents and deaths result from the explosion of fuel tanks in the planes, like when two planes collide, or when the plane falls on the ground.

With the advent of technology, i wonder whether it is possible to prevent the fuel explosion.

Can this be done by evaporating the fuel in the planes just before the collision?
Or use a solid architecture encapsulating the fuel tanks in the planes, such that the fuel is not set to fire?

What research has been done in this field and if so what were the findings?

"We know that most of the plane accidents and deaths result from the explosion of fuel tanks in the planes"
This is a fallacy. Most deaths don't happen because of explosions, but because of impact damage, fire, and inhalation of toxic fumes (in no particular order).
Next to that, many people tend to get killed because they are crushed by fellow passengers during evacuations. And some die on the ground being run over by emergency vehicles or from environmental conditions (heat, cold, wildlife).
Ratchet Freak correctly points out why your "solutions" won't work (in fact one of them will make the problems worse). And yes, research is being done and has been done. Modern jet fuel has a much higher flame point and vapour pressure than does regular gasoline as a result. Fuel tanks are fitted with baffles and sometimes coolers to keep the fuel liquid so it doesn't explode easily. This is in part a result of what happened to TWA800, one of the very few accidents to be caused by a fuel tank explosion (and there the explosion was itself only possible due to a combination of rare circumstances and chance events, made worse by maintenance problems with the aircraft).
The image of aircraft (and cars, trains, ships, buildings, anything really) blowing up in a wall of flame at the least trouble is one created and perpetuated by Hollywood and has no reflection in reality whatsoever.


How does yaw relate to pitch? I have been confused about the relation of yaw and pitch in propeller powered aircraft. When such an aircraft is pitching up, will it yaw to the left or right? Conversely, when it's pitching down, which way will it yaw?

When I try this out on X-plane, the plane turns left when I take off. However, some online material insists that the plane will yaw to the right when I am pitching up. This is confusing me. What's the best explanation for this?

How does yaw relate to pitch?

There are four forces at play on a single engine aircraft that can cause turning tenancies or Yaw.

The main reason a single-engine propeller aircraft yaws left at T/O is due to  Asymmetrical Thrust (P-Factor). At high angles of attack the right side of the propeller disc creates more thrust than the left side and this causes Yaw to the left.

Gyroscopic Precession causes a yaw to the right when an aircraft is suddenly pitched up(tail is lowered or nose is raised) and a yaw to the left when an aircraft is suddenly pitched down. (tail is raised or nose is lowered).
This force is only apparent while the aircraft's Pitch is changing, once the pitching action is stopped, the force is gone. (not present in a steady nose up climb)

Slipstream effect causes a slight yaw to the left, and slight roll to the right.

Engine torque causes a roll to the left.

Most single engine aircraft today have a clockwise spinning propeller. All these forces would be the opposite if it were a counter-clockwise spinning propeller.

A more detailed explanation can be found here: Turning Tendencies


Why did most WWII Allied piston engines not use fuel injection? One would think that given the huge push for ever more performance and reliability on piston engines during the heat of WWII would push the designs to their absolute limits, however, most American engines seem to be comfortable with the old carburetor technology which is prone to icing, hiccups and perform poorly under high Gs. Reading the literature of how Pratt & Whitney optimized the Double Wasp to an extreme (to the extent that the crankshaft is taking so much force that it needs a pair of torsional dampers even after forging) is quite jarring when one comes to realize it still uses the good old carbs to suck in fuel, when at the other side fuel injection was adopted eagerly.

Those engines didn't use carburetors as in gravity operated float carburetors.  They used "pressure carburetors".  Pressure carbs are mechanical fuel injection systems that inject the fuel from a single point at the start of the manifold instead of injecting fuel at the intake port via a distribution system.  Not quite as theoretically efficient as point fuel injection, but it has all the other advantages including automatic mixture control and no G sensitivity, as well as being less sensitive to damage by not having small high pressure fuel lines running to each cylinder.

On cars in recent years you had a similar system called "throttle body fuel injection", more or less an electronically controlled pressure carb.


How should I interpret the Douglas DC-4 approach climb performance chart? Can someone explain what "C = .04 Vso2" means as the "denotes required rate of climb?". I assumed the point at 6500 ft altitude and 60,000lbs landing weight will mean that the required rate of climb is within the limitations but after calculating this to an approach climb gradient, the answer does not require the limitation of a minimum approach climb gradient of 2.7%.

So the main question is: What does the dotted line mean and what has the C = .04 Vso2 has to do with it?

I interpret the dotted line to indicate the conditions needed to meet the minimum required performance, as specified in CAR1 (the certification standards used when the DC-4 was originally built.). Conditions to the right of the line are "Good", to the left of it are "No Good".  I.E. if you had a gross weight of 60,000 lbs, and were configured as specified, the aircraft would not be able to meet the required performance at any altitude above ~6400 Ft.

I believe the "C=blah etc" statement is referencing the airspeed used to determine these performance results. C= Calibrated Airspeed, VsO² is stall speed in this specific configuration, and I'm guessing that the ".04" means 4% above said stall speed.

I hope this has only confused the question tremendously, and as solely my opinion, is worth precisely what you have paid for it. YMMV. Do not attempt at home. This offer not valid.


Where can I obtain official German VFR approach charts? I am looking for the official VFR approach charts of German airports. I could found a preview here : airports.de however I do not know where I can find the official ones or where I can order them. This would be useful to purchase the  maps only for the  airports I am interested. Any suggestion?

The official German AIP VFR is only distributed via a company called Eisenschmidt. I'm not even sure, there's a digital version of the official charts. But you can buy a 2.35kg heavy print version of the VFR AIP. The only thing that comes close to the charts digitally is something called "VFR eBulletin", a software, where you can enter your route and see that overlaying an ICAO map - but the map is in very bad resolution and low quality.

Sadly, Germany doesn't do it like many other European countries by publishing their AIP VFR online for free.


How are north and east compents of the wind calculated, given a wind speed and direction? I have a wind speed and wind direction of an aircraft. I need to find wind component along the true North axis and East axis.

Can anyone explain me how to do that?

Say wind speed is the hypotenuse in the Right angled triangle and angle is wind direction. How to find wind speed along north axis and east axis?

Simply use trigonometric functions:

$V_{north} = -V \cos \theta $

$V_{east} = -V \sin \theta $

$V$ is wind speed

$\theta$ is wind direction clockwise relative to the true north (e.g. east is 90°). Note that wind direction is typically given as the direction from which the wind is blowing. If you have a wind direction that in given into the direction of air flow, then you should remove the minus signs from the formula's above.


How much compensation does an unruly passenger have to pay to an airline if the flight has to be diverted to remove them? If a passenger becomes unruly and the captain decides to land and remove that passenger from the flight, how much does the passenger have to pay the airline for the cost?

In addition, what are the reasons for flight crews to decide whether to divert or continue the flight?

Unruly passengers can face the following:

Monetary fines
Prison sentences
A ban from that airline

Excerpt from Wikipedia:

  In the United States, passengers who disrupt the duties of a flight
  crew member can face fines up to $25,000 and sometimes lengthy prison
  sentences.

IATA has a policy for these passengers mentioned here, and more information is here.

ICAO has a detailed document on unruly passenger prevention and management. They have adopted a new protocol to amend the Tokyo Convention.


What is the possibility of a depressurization emergency during a commercial flight where all or some of the oxygen masks fail? Can we calculate this? Or is it almost impossible?

The oxygen system for passengers in an airliner is generally powered by a chemical oxygen generator.
The generator contains chemicals, which when they come into contact with each other, commence a reaction that produces oxygen for a few minutes.
The act of pulling down the mask triggers the contact between the chemicals.
A generator typically serves two or three seats, and each generator is independent of the others on the aircraft. They are not part of a single system with common points of failure.
The panel behind which the masks is opened by a pressure switch, and can also be opened manually.
However the crew will use bottles of oxygen, and the flight crew will use a more complex system that also includes smoke hoods.
Conceivably (anything is possible) a manufacturing fault or sabotage could render every single one of the generator/mask sets inoperative, but it would be an extraordinarily unlikely thing to happen.
People often imagine a system of pipes carrying oxygen to all the masks, but in fact such a system is rarely used. One notable example is the earlier (-100 to -400) variants of the Boeing 747, in which the oxygen is indeed piped. And, apparently, may have not always worked as expected:

The flight crew donned their oxygen masks and manually deployed the passenger oxygen masks.
[...] The PIC was also advised that there appeared to be no oxygen flowing through any of the passenger cabin oxygen masks, however this did not seem to have had any ill effect on the passengers. After the PIC cycled the passenger oxygen switch, a momentary surge of oxygen through the passenger masks was observed.

(from an Australian Transport Safety Bureau report into a November 2001 incident)


Why has the range of movement of the control surfaces changed over the past year? During the annual inspection on our glider, we discovered that the maximum downwards extension of the right aileron (i.e. full left stick) was outside the manufacturer's tolerance. The measured value was 32mm and the manufacturer allows 40mm ± 5mm.

What are the possible causes of a change in the geometry of the system such that the ailerons no longer move in the range they did last year?

For reference, the glider is a 1983 Schleicher ASW19b, with standard l'hotelier control connections and aluminium push rods over bell cranks in the fuselage and wings.

We found the problem. The control stops are under the seat and are made of plywood. It looks like at some point in the past someone had added a small layer of plywood to reduce the control deflections but that over time the glue had deteriorated or the wood had swollen, so that there was now too much stop. Removing the extra ply and sanding the glue back to the wood fixed the problem.


Can you help me identifying this WW1 German or Austrian airplane from my photo collection? Can anyone help me to identify this WW1 aircraft?

It looks as though it reads Otto No. 202 on the plane.

@DalamaniSingh is correct, but the people who built and flew this plane never called it "Otto pusher".

Gustav Otto was one of the seven children of Nikolaus Otto, who designed the first practical internal combustion engine and after whom the Otto cycle is named. He started an aircraft factory in 1909 near Munich and later relocated north to Oberschleissheim. The first product of this factory was simply called "Otto Doppeldecker" (Otto biplane). It was produced from 1912 to 1915, but was obsolete by the time WWI started. The plane was mostly used for training. The factory had to close in 1915 and the historic building now houses a collection of aircraft and has become a museum. In the attached restoration workshop, a replica was built recently.


Can an aircraft (civilian or military) land with its brakes already engaged? Can an aircraft land with its brakes already engaged at the max landing speed of that aircraft?

Can an aircraft land with its brakes already engaged at the max
  landing speed of that aircraft?

Yes...

Im gong to assume that by brakes engaged you mean to full, preventing the wheels from spinning. First Lets consider the two different types of planes. Tail wheel planes will most likely nose over depending on how the plane is landed. A tricycle gear equipped plane will most likely grind through the main gear. Remember the nose gear does not generally have a brake (in my GA experience it never has a brake).

Although I would not advise it. It depends really what you mean by "can it land" it will touch down and the tires will simply lose traction and start skidding (eventually to a stop). The results (on a dry runway) may be similar to what we saw with JetBlue flight 292 which had its nose gear turned 90 degrees. The gear was basically ground through like it was sanded down. The tires in this case will all begin to heat up severely and eventually fail. My guess would be that the skidding will vary from side to side and cause the plane to weather vane quite a bit as if differential braking were used.

You may also damage the runway quite severely.


Is there an aerodynamic force that would keep this experimental WW2 era prop from flying as fast as an early jet? The XB-42 was an experimental bomber developed during WW2.  Its twin engines delivered a combined 3,800 HP and top speed of 410 mph at 23,440 ft.

It's an amazing aircraft.  But if an enormous aircraft is that fast why not use the same concept for smaller fighter-sized aircraft?  I assume there must be a good reason because it didn't happen.

I used a modified version of the drag equation found on NASA's website to estimate the speed increase if the front profile was reduced by 50% and everything else stayed identically the same.  The modified version can be found here.

By reducing the front profile by 50% the top speed increased by 25.99%.  That brought its top speed up from 410mph to an amazing 517mph.  That's almost as fast as a jet.
Is that possible or am I missing some other aerodynamic force that would stop the plane from approaching that speed?

I guess at the most basic level is this concept correct?

Smaller frontal area = faster top speed.

Is there some other aerodynamic force that would negate that?

Answer to comment below: Zeus answered that reducing the aircraft's profile wouldn't make a significant difference because most drag was produced by the wing.  Yes and no.  Wing lift does produce a lot of drag at low speed but that drops as the plane accelerates.  At high speed nearly all drag is parasitic (i.e. the shape of the aircraft) as evidenced by the chart below.  Moreover my question was theoretical.  If 50% of the plane's profile was removed the weight could be removed as well and with it the wing size.  Turning the XB-42 airframe into a small, fighter aircraft was the general point of the question.

First of all, there were several propeller aircraft which were much faster than the XB-42. But let's stick with it and scale it to see where that brings us.

For that we need two things: Equations for drag $D$:
$$D = \frac{\rho\cdot v^2}{2}\cdot S\cdot\left(c_{D0}+\frac{c_L^2}{\pi\cdot AR\cdot\epsilon}\right) = \frac{\rho\cdot v^2}{2}\cdot S\cdot c_{D0}+\frac{(m\cdot g)^2}{\pi\cdot AR\cdot\epsilon\cdot\frac{\rho\cdot v^2}{2}\cdot S}$$
and for thrust $T$:
$$T = \frac{P}{v}\cdot\eta_p$$

The symbols are (values are for the XB-42 at 7,140 m):
$\kern{5mm} \rho\:\:\:\:\:$ air density = 0.581 kg/m³
$\kern{5mm} v\:\:\:\:\:$ velocity = 410 mph = 183.3 m/s
$\kern{5mm} S\:\:\:\:\:$ wing surface area = 51.6 m²
$\kern{5mm} c_{D0} \:$  zero-lift drag coefficient
$\kern{5mm} c_L \:\:\:$  lift coefficient
$\kern{5mm} \pi \:\:\:\:\:$  3.14159$\dots$
$\kern{5mm} AR \:\:$  aspect ratio of the wing = 8.95
$\kern{5mm} \epsilon \:\:\:\:\:\:$  the wing's Oswald factor = 0.9
$\kern{5mm} m \:\:\:\;$  aircraft mass = 15,000 kg
$\kern{5mm} g \:\:\:\:\;$  gravitational acceleration
$\kern{5mm} P \:\:\:\:\:$  engine shaft power = 3800 hp = 2833.66 kW
$\kern{5mm} \eta_P \:\:\;$  propeller efficiency = 0.85

In order to determine the unknown zero-lift drag, drag is set equal to thrust, the values above are inserted and the equation is solved for $c_{D0}$:
$$c_{D0} = \frac{\frac{P}{v}\cdot\eta_p - \frac{(m\cdot g)^2}{\pi\cdot AR\cdot\epsilon\cdot\frac{\rho\cdot v^2}{2}\cdot S}}{\frac{\rho\cdot v^2}{2}\cdot S} = 0.02272$$
which looks about right.

Then we need some clever formula how mass will change with a scaled airframe. Since both the engine and the pilot will stay constant, to assume that mass will scale with the square of the length is quite generous. So we have a second aircraft of 70.7% size which will have half the frontal area, half the mass but the same power. Now we need to solve for the unknown speed with the now known zero-lift drag:
$$v^4 = \frac{2\cdot P\cdot v\cdot\eta_p}{\rho\cdot ½\cdot S\cdot c_{D0}} - \frac{(2\cdot ½\cdot m\cdot g)^2}{\pi\cdot AR\cdot\epsilon\cdot\left(\rho\cdot ½\cdot S\right)^2\cdot c_{D0}}$$
$$v^4 = 14.144.659.448\cdot v - 167,497,545.8$$
$$v = 237.76\:\text{m/s} = 531.85\:\text{mph}$$

Now all what is left to be solved is how to squeeze the existing engines and their cooling system into half the fuselage cross section.

  I guess at the most basic level is this concept correct?

To answer your question directly: I used a slightly different approach and got an even higher speed. If I leave mass constant, the higher induced drag will limit the speed to 223.37 m/s, which is just shy of 500 mph. I wonder how you got a speed of 517 mph. The car example on the linked site does not include induced drag, so I guess your concept needs a little improvement.


Logging time towards commercial pilots license I am in a part 141 program trying to finish up my commercial pilots license. The airport we operate out of will be closed for a few weeks so I was wondering if I'd be able to rent a plane close to where I'm from to knock out some of the solo hours I have left. It wouldn't be a school plane and my instructor wouldn't be with me. Is this possible?

I am assuming that you are already a private pilot working on your commercial ticket. There is no requirement to do your solo hours at one flight school. Just make sure your primary instructor knows what you are doing and is OK with it.


How can using split throttles help when landing twins in crosswinds? In General Aviation light twins, when landing in heavy crosswinds, what are some considerations to using asymmetric (or Split) throttles to induce a sideslip, to align the fuselage with  the ground track and the runway centerline instead of rudder?

I was told that this technique allows the aircraft to track down the runway centerlines with fuselage aligned with the runway without as much bank angle into the crosswind as would be required with symmetric thrust using cross-controlled rudder and opposite aileron alone.

I was thinking that the need for bank into the crosswind is due to the  need to compensate for the sideslip force (from the yaw due to downwind rudder) which would otherwise (without the bank) turn the aircraft downwind.

But it seems to me that using asymmetric thrust to induce the same sideslip would produce the same tendency to turn if the wings were not banked into the crosswind to compensate. Why not??

The use of asymmetric thrust when landing a twin in a crosswind effectively accomplishes the same thing that rudder input does.  It induces a yawing moment about the aircraft’s vertical axis, the same as pushing on the rudder pedals does.  It helps to alleviate excess rudder pressure on the flight controls during the approach, making it a little more comfortable for the pilot to fly the approach. You are still required to apply aileron input into the wind in order to hold the runway centerline.   Using asymmetric thrust during a Crosswind Landing does not alleviate aileron pressure or required bank angle to track the runway centerline.


How to calculate required thrust for take-off knowing gross weight and L/D? I know that many variables play into the required thrust for a take-off and for climb. Most of those specs boil down to a targeted gross weight, wing loading and L/D ratio. Intended flying speed range is also known but probably not even needed for this estimate. Using these specs then I can roughly assume that many specs have been taken into account for a thrust calculations.

For ex. aircraft is gross weight 400 lb with L/D ratio of 10. Assuming a non-accelerating level flight at optimal cruise speed 50 mph in no wind condition it will require at least 400 / 10 = 40 lb of thrust.
Based on above numbers how to make rough estimate of the minimal thrust required for a reasonably short take-off (say within 500 to 1,000ft roll of runway) ?

Note: please keep in mind I am familiar with many other conditions and aircraft specs affecting the required thrust. Yet for 100 years practical aircraft designers used very simple math approach to estimate needed thrust. I personally knew one of old generation designers who did this well in many of his successful designs using simple math dealing with few numbers (he passed away years ago). He only used gross weight, wing loading and targeted L/D ratio chosen from his experience.
Please share if you know the answer.

http://www.dept.aoe.vt.edu/~lutze/AOE3104/takeoff&landing.pdf

This source has been really helpful for me in calculating takeoff time and takeoff distance. In this method, the author uses thrust as an input to calculate takeoff distance, but obviously you could re-arrange the equations to calculate for thrust if you knew the other variables. You will likely need to know the static thrust (zero speed thrust) of your engine and then can calculate for thrust required at takeoff. I would recommend putting the equations into an excel spreadsheet where you can then play with all the inputs until you reach a desired result. Hope this helps!


When are winglets most effective? If winglets reduce induced drag, induced drag is greatest at slow speeds. When are winglets most effictive?

At low speeds.  This is why you see them on jet airliners, which cruise a low "indicated" airspeeds, just low enough that the vortice strength is enough to get a decent lift vector out of the winglet from the flow.  An airliner cruising at M.78 say, at FL380, is only going about 2x its flaps up stall speed.  A straight wing airplane at 20000 ft cruising at 250 kt might be going 2 1/2 to 3x its flaps up stall.  The vortices aren't strong enough in that case and you see them on straight wing airplanes rarely, and if you do it'll be to improve rate of climb more than anything, or maybe simply "styling".


What are the main differences between Flares and Chaff? Over the years I've heard the two used almost interchangeably but after watching some videos it would seem that they each have specific and particular functions.

Both chaff and flares are defensive countermeasures deployed by military aircraft. The purpose is to confuse radar-guided or infrared-guided anti-aircraft missiles fired so that they can divert.
A good definition about them is here:

Chaff is composed of millions of tiny aluminum or zinc coated fibers stored on-board the aircraft in tubes. When an aircraft is
threatened by radar tracking missiles, chaff is ejected into the
turbulent wake of air behind the plane.
Flares are used to distract heat-seeking missiles. Most are magnesium pellets ejected from tubes to ignite in the wake behind the
aircraft. These flares burn at temperatures above 2,000 degrees
Fahrenheit, hotter than the jet engine nozzles or exhaust and exhibit
large amounts of infrared light.


Is gravity less on an airliner at cruise altitude? Is the force of gravity less on an airliner at cruise speed and altitude? I'm not talking about a special reduced gravity flight with a parabolic flight path, just a typical long distance flight.

Seems to me there should be less as passengers are further away from the centre of the earth, and also possibly a tiny effect from the speed the plane as it travels round the curve of the earth (altitude remaining constant) but does anybody actually know how much less?

There is less gravitational force, but by how much? An insignificant amount.
The gravitational force of attraction between two objects is given by,

$\displaystyle F_{\mathrm g} = \frac{G m_{1} m_{2}}{R^2}$,

where,

$G$ is the graviational constant,

$R$ is the distance between the object's centers, and

$m_{1}$ and $m_{2}$ are the masses of the objects.

Instead of finding the variation in force between the aircraft and earth, it would be be better to find the variation in the acceleration due to gravity, $g$ (as $F_{\mathrm g} = m_{\mathrm a} g$, with $m_{\mathrm a}$ being the mass of the airliner)

We have, on earth's surface,

$\displaystyle g = \frac{G m_{\mathrm e}}{R_{\mathrm e}^2}$

where,

$m_{\mathrm e}$ is the mass of the earth, and

$R_{\mathrm e}$ is the radius of the earth.

For the aircraft at an altitude $h$ above the surface of the earth, this becomes,

$\displaystyle g_{h} = \frac{G m_{\mathrm e}}{\left(R_{\mathrm e} + h\right)^2}$

Taking ratio, we get,

$\displaystyle \frac{g_{h}}{g} = \left(1 + \frac{h}{R_{e}}\right)^{-2}$

Plugging in numbers, we get, for an airliner cruising at 12 km,

$g_{h} = 9.773\ \mathrm{m\ s^{-2}}$,

or about 0.37 % less compared to the sea level value. This is quite small and would not be noticable to all but the sensitive instruments.


What angle of deflection / pitch on the rotor blades can the controls generate? I was wondering, if a pilot uses full input on cyclic and collective, what pitch angle can be achieved for the rotor blades? Is there a mechanical stop to prevent extreme angles of attack? And how would that interact with the blade pitch needed for auto-rotation?

Thanks!

Maximum pitch angle would totally depend on the type of helicopter you are flying. Each helicopter has its own set of limitations and pitch angles depending on the blade, rpm, etc. The controls include a mechanical stop, and you would hit that limit sooner or later if you put in an overly aggressive control input on the cyclic, or full collective up or down. Think of it as the same way you would hit the outside edge of the control on a video game joystick.

In "real life", the pitch angle numbers are irrelevant to a helicopter pilot. During
autorotation, the RPM of the spinning blades is maintained by reducing the pitch angle allowing an upflow of air from the descent to maintain the rotors spinning - similar to blowing air on a fan in order to keep the fan blades moving. The rotor RPM can be adjusted through up and down collective movements, which will in turn increase or reduce the RPM required.


How many checklists are there for a commercial pilot for the entire flight? I wanted to know the number of times a pilot has to refer to his/her checklist for the entire flight (before startup to engine shutdown).

Typically, the checklists in normal operations are:

External walk around and preflight
Before start
Before taxi
Before take-off
After take-off
Cruise
Descent
Approach
Landing
Shutdown
Secure

This list is pretty much the same for all aircraft.

Normally, each checklist is only used once at the appropriate time but a wise pilot would re-run a checklist if interrrupted.

For example, you are cleared to start and complete the before start checklist but there is then an unexpected delay before you actually start.  You wait for 30 minutes.  No need to redo the before start checklist because you did it earlier?  No, do it again.  Something might have changed.


What is the difference between SoCal Approach, SoCal Departure and SoCal TRACON? I've heard these 3 terms in ATC recordings and on web pages. Do they all use the same frequencies and the same controllers?

SoCal TRACON (Terminal Radar Approach CONtrol) is the name of the facility.
SoCal Approach and SoCal Departure are the call signs used over the radio by that facility, depending on whether the particular aircraft they’re talking to is arriving or departing. They’re the same controllers on the same frequencies.


Why do cargo aircraft still have floors? Even with dedicated cargo aircraft built as cargo aircraft (rather than converted from a passenger-carrying configuration), the cabin is virtually always still divided into an upper and a lower lobe (which would, on a passenger aircraft, be the passenger cabin and the cargo hold, respectively) by a floor located a third to a half of the way from the bottom of the fuselage, drastically reducing the maximum size of the cargo that can be carried and making it much harder to transport round outsize cargo (such as, for instance, large high-bypass turbofan engines as are used on essentially all modern jetliners) by air.  Given that the essential structural members of a large modern jet are

the skin itself;
longitudinal longerons running the length of the fuselage just beneath the skin; and
circumferential frames encircling the fuselage just beneath the skin;

it should be possible to remove the floor, and thus dramatically increase the freighter's ability to carry very large objects, without significantly compromising the fuselage's structural integrity (the middle of the cabin would still be partially occluded at the bottom - or the top, or the middle, depending - by the center portion of the wingbox, but there would, nevertheless, be a considerable increase in the outsize-cargo capacity ahead of and behind the wings).  Why isn't this done?  Is the floor left in to facilitate possible future conversion to a passenger aircraft?

Because the overwhelming amount of cargo is fairly small and floors allow easy loading of both decks at the same time which is more important than the ability to load big cargo on occasion. By having floors you can load standard cargo containers quickly and efficiently. It also gives you the ability to standardize the containers with a reasonable degree of reuse most importantly they can fit into the lower deck of a passenger aircraft with out modification. Passenger airlines make a lot of money moving commercial cargo.

When it comes to flying around big, cumbersome cargo there are simply aircraft designed and built for such a task like the Airbus Beluga

(source)


Is there a universal departure recovery procedure? Let us say you're in a non-fly-by-wire tactical aircraft (say a F-15 or an A-4) doing maneuvers in the local MOA, and you manage to depart the jet in some non-spin fashion.  Is there a standard procedure for recovering the jet to controlled flight, analogous to how there are standard spin recovery procedures, or is the first step on the checklist "eject"?

The answer depends on the aircraft. In most cases it is No, but for some it is Yes.

The MiG-29 has a green button at the right side of the stick which recovers the aircraft to a wings-level, shallow climb attitude if pressed. Note that the MiG-29, unlike its Western counterparts, is aerodynamically stable over the full angle of attack range beyond 90° and the flight control system can recover the aircraft from any attitude, altitude and thrust permitting.

Here is a quote from someone reporting his experience of flying a Malaysian MiG-29 (link)

  The stick has a red autopilot button on the left and a green auto
  recovery switch on the right for the disoriented pilot, and works by
  pressing the green panic button. The system recovers the jet to wings
  level and places the airplane in a slight climb if energy is
  available. This system is known to be reliable but is not often used.
  This is most likely due to the necessity of having to recognize that
  you are spatially disoriented prior to pushing the auto recovery
  button.

MiG-29 cockpit (picture source). The green button is clearly visible.


What are the meanings of these terms used in ATC ground communications? Regarding ATC ground communications, what/who are the following callees? Are these aircraft, or vehicles, or people?

[Airline name] maintenance
[Airline name] tug
[Airline name] mechanic

If you are driving a vehicle anywhere within the movement controlled area of an airport you need to be in contact with the ground controller.
1 & 3 are virtually synonymous, it is a person, a mechanic, working for the named airline's maintenance department, driving a vehicle.
2 is a person driving a aircraft tug vehicle.


Why is the Tu-204 virtually immune to wing and tail icing? Atmospheric icing is extremely hazardous to heavier-than-air aircraft, as it badly disrupts their ability to generate aerodynamic lift (the inherent roughness of accreted ice encourages the airflow to separate from the upper surface of the wing, causing the aircraft to stall at a much lower angle of attack, and a much lower lift coefficient, than it would otherwise) and greatly increases aerodynamic drag (the rough, non-streamlined surface of the ice has much the same effect on the aircraft’s motion through the air as gluing a big sheet of 00-grit sandpaper to your butt would have on your motion down a playground slide).  As such, built-in anti-ice equipment (generally consisting of heaters using either engine bleed air or electrical-resistance heating elements, or of pneumatic deicing boots that mechanically dislodge ice) is generally a must for the wing(s), tail surface(s), and propeller(s) (if any) of airplanes intended to fly in icing conditions, in order that any accumulated ice can be melted or broken off before it can significantly affect the aircraft’s aerodynamics.  If these systems are inoperative, the aircraft must not be flown in icing conditions until its anti-ice capability is restored, and aircraft lacking these systems are generally forbidden from entering ice altogether.
The Tupolev Tu-204 is an unusual exception to this.  Its wing and tail surfaces are (supposedly) so resistant to ice accumulation that it can fly in heavy icing conditions without needing to be equipped with wing or tail anti-ice equipment:

...The wings and tails are relatively resistant to ice build-up, and as such anti-icing systems are not equipped.  Among today’s airliners the Tu-204 is the only one which does not require wing anti-icing systems.  During the test flight safety has been confirmed without the anti-icing system on the bearing surfaces and the aircraft obtained Russian and European certificates...  [Wikipedia, “Tupolev Tu-204”, section 1.1 (“Technology”).]

This seems like a rather suspect claim; atmospherically-generated ice has the well-documented tendency to stick to essentially whatever it hits (as long as it’s not warm enough to melt the ice off), no matter what its composition, shape, or surface texture.  Even if the Tu-204 goes the usual route of making the tail bigger so it works fine even when iced, this doesn't explain how they can get away with non-anti-iced wings; how does the Tu-204 supposedly manage to do this?

Just like Teslas, being designed in California, perform worse in ice and snow than Volvos, Russian airplane designers pay more attention to icing than Western ones, where efficiency is paramount. And you can design for icing, mainly by selecting a large leading edge radius which keeps suction peaks low. In addition, large airplanes are proportionally less susceptible to icing.
From NASA:

Wings that are thin or have sharp leading edges are more efficient ice collectors. For this reason, smaller, thin airfoils may accrete more ice faster than larger, thick airfoils. A large transport aircraft will accrete proportionally less ice than a smaller aircraft traversing the same icing environment.

Also, if the leading edge radius of the wing decreases from root to tip (as it frequently does in swept or tapered wings), the ice accretion will be proportionately greater near the tip. When contaminated with ice, wings with this design may experience flow separation at the tip before the root. Note that this is exactly opposite the way clean wings are typically designed to experience flow separation. Thus, when you fly these types of aircraft, you could lose aileron effectiveness before total wing stall, increasing the probability of an uncommanded roll and greater difficulty in regaining control.

A further factor is the thrust margin of airplanes. Being a two-engined airplane, the Tu-204 has plenty of excess thrust to compensate for the addd drag of iced wings. Since icing occurs at moderate altitudes, the thrust margin there is considerable. The same is true of the B777 and the A330, of course.
But much is left to trial-and-error. Again NASA:

Some aircraft seem to be more susceptible to airframe icing than others. The reasons for this are not well understood and probably involve multiple factors. For example, there seems to be a complicated interaction between the details of the wing design (e.g., taper ratio, twist) and its relation to the fuselage.

And in Russia icing research is well established. From the website of the Central Aerohydrodynamic Institute (TsAGII)

In Central Aerohydrodynamic Institute named after Prof. N.E. Zhukovsky (part of Zhukovsky Institute National Research Centre) the considerable attention is paid to icing effect made on aerodynamics, stability and controllability of aircraft.

The T-101 windtunnel of TsAGII in Zhukovsky is specially equipped for icing studies and has been used in the design of most Russian airplanes. I could not find a confirmation but would be surprised if the Tu-204 basic design has not been extensively studied there.


What is Vg in this VG diagram? There are two vertical bars beyond Vne labelled: @800#-Vg = 150MPH and @840#-Vg = 147MPH. These lines represent Vg at two different weights.

Can you tell me what  Vg is, where it's officially defined, and how it's calculated?

It is the maximum speed in gusty weather. Aircraft designers and certification authorities make assumptions about the maximum vertical gust an aircraft will encounter and design the strength of the wing spar for it. Here 24 feet per second are assumed.

Depending on the mass of all parts not creating lift (fuselage, vertical tail, pilots, equipment ...) the load on the wing spar varies with the aircraft mass. For that reason, lighter aircraft can afford to enter a gust at a slightly higher speed. Here, the 800 lbs glider may fly up to 150 MPH, while the 40 lbs heavier glider should stay below 147 MPH to suffer the same wing spar bending loads when flying into this 24 fps gust.

Flying faster means flying at a higher dynamic pressure and at a lower angle of attack. Entering a gust will increase the angle of attack by the ratio between gust speed and flight speed. Since dynamic pressure is proportional to the square of flight speed, a linear wing lift increase due to higher flight speed will remain when entering a vertical gust. Also, at lower speed the angle of attack might be high enough that the angle of attack increase due to the gust will stall the wing, putting a natural limit on the load increase. Flying faster will remove this load limitation.

The maximum flight speed in gusty weather v$_g$ is a limit speed just like v$_{NE}$, but applies only in specific weather conditions (admittedly those which are most suitable for glider flying). While v$_{NE}$ might be determined by a minimum flutter margin, a formula in the certification requirements or structural loads in maneuvers, v$_g$ is determined by the maximum load factor the aircraft can tolerate.


How are fixes used during an approach? When I read through IFR materials online, or when I hear pilots talking about approaches, they often talk about using fixes to get to/through the approach.

Two questions (closely related):

Firstly, just to make sure I completely understand, what are fixes in this particular context?
Secondly, how are they used when a pilot is using a particular approach?

What a fix is has been answered here but for now let's just say it's a known location that a pilot can navigate to if he has the right equipment. Fixes are shown on various charts and approach plates.

As for using those fixes on an instrument approach, there are lots of variations and details but again, let's ignore most of that for now. The basic concept is very simple:

Fly to an Initial Approach Fix (IAF)
Fly to other fixes as needed to execute the approach
Land (or go missed)

For example, here's the RNAV (GPS) 36R approach at KHSV:

You can see at the bottom of the map portion of the plate that both MASHA and FEWER are IAFs, so that's where the approach starts. Let's say you're approaching from the south-west and you've already descended to a reasonable altitude for starting an approach, following a STAR or vectors from ATC.

ATC says something like "N12345 proceed direct MASHA, cleared for the RNAV 36R approach". That means that you are now cleared to execute the approach as shown on the chart, with no further instruction from ATC (although they might have vectored you towards the IAF initially).

The chart tells you that at MASHA you need to be at at least 3000ft MSL so you simply fly there at or above that altitude. Since it's a GPS approach, you load it and activate it in your GPS unit, and you can follow the GPS track to MASHA.

After MASHA, the next fix is ENIKY and the GPS track will lead you east to that fix (which is a heading of 091° from MASHA). The profile view at the bottom of the plate shows that you must still be at or above 3000ft at ENIKY. Then you turn left to 002° and fly to UJOTY, where you must be at or above 2700ft. Then you continue to GEPDE at or above 1180ft. Then you land :-)

Of course, I'm ignoring a huge amount of detail here - like everything else printed on the approach plate! - but since this question is about fixes the main point is that they're simply a series of waypoints that you fly over (or past) to get to the runway. And obviously you also have to control your altitude as you descend, but the altitude is defined by the approach procedure, it isn't part of the definition of the fix itself. The same fix can be used in multiple approaches: MASHA and FEWER are also the IAFs for the RNAV (GPS) 36L approach).

Even though different approaches define and use fixes in different ways, the basic idea is always the same: just fly from one fix to the next until you get where you're going.


How do you sump fuel when it's raining outside? I've been taught to always sump the plane's fuel system before going flying to check for water / contamination / proper fuel grade. However, I've yet to go flying in rain. What's the proper procedure to drain fuel during rain? If I took the fuel cap off to dump the fuel back into the plane, I'd be worried about rainwater getting in the tanks.

AOPA has a good article about checking fuel:

  ... check the fuel caps and replace worn, brittle, or cracked seals
  that can allow rain to seep into the tanks.

You cannot be 100% that the fuel does not contain any contamination. If you risk that by putting the sample fuel back in the airplane (debatable topic) will add more water in the tanks, then simply don't do it.

I guess since many flight schools offer wet rentals, they don't want to waste a drop of fuel. But it is okay to do that, so that their aircraft and your life are safer.

Update

There are many arguments about putting sump fuel back in the tank. Many people say that a GATS Jar is there to capture the contamination and then you can put it back in the fuel tank. In Cessna training material, they use a container where you can put sump fuel. At many places, there is a fine for throwing it on the ground.

So in case of rain, the best option is to put in such a container. However, if it is raining that hard with strong gusty winds, I am sure taking care of sump fuel should not be your problem.


How do I calculate the centre of gravity on the lateral (transverse) y-axis? I have a real issue with determining the centre of gravity for the y axis of an aircraft, especially with selecting the reference/datum point and how to measure the displacement. Please I would really appreciate any form of help I can get.

Transport airplanes have lateral C of G limits in terms of x distance from the centerline, but this only a certification requirement (related to roll authority in a critical case situation) and is only expressed for the flight crew as a fuel imbalance limit, fuel being the dominant factor, and is not accounted for in weight and balance data that the crew uses to determine if loading is correct.
The datum is the x=0 axis, with the C of G to the left, on, or right of it.  To calculate it, you would need an empty lateral C of G position, determined by weighing the airplane and working out the empty C of G offset to left or right of the x axis based on the weight difference between the left and right main gear weighing points, and the distance of those points from x.
Then you can add fuel and passengers and calculate the change if any to the lateral C of G. Since the passengers are normally randomly distributed on the left and right side of the cabin, the passengers can normally be considered neutral. Then it's only the effect of an unequal fuel load.
But as I said, for practical purposes, the fuel imbalance limits in the airplane's operating limitations account for the requirement to stay within maximum lateral C of G limits, and it's not necessary to calculate it.


What restrictions are there to building a tower near a private airstrip? I'm exploring the possibility of putting up a radio tower on a property I own. The problem is that my property is roughly 1,000ft from a private airstrip. The location that I want to put the tower is not within the approach/departure path of the runway and is not under any navigational easements. The height that I'm looking at is roughly 150ft, just high enough to get approximately 20-30ft above the existing trees in the area. My question though is, what are FAA restrictions around building towers near private airports? Is it different from public airports? If so, is it possible to do this at all so close to an existing airport?

According to this AC you dont need to light the structure,

  Any temporary or permanent structure, including all appurtenances,
  that exceeds an overall height of 200 feet (61 m) above ground level
  (AGL) or exceeds any obstruction standard contained in 14 CFR Part 77
  should be marked and/or lighted.

But the FAA does have special cases and since you are close to a strip they may require/recommend it,

  The FAA may also recommend marking and/or lighting a structure that
  does not exceed 200 (61 m) feet AGL or 14 CFR Part 77 standards
  because of its particular location.

Looks like you need some specific stuff to actually light it. Your local FSDO should be able to help out with what ever info you need. As far as I know these kinds of regulations don't change between public and private airports.

You can find the letter of the law for 14 CFR Part 77 here. The most applicable to your case is quite possibly,

  (3) A height within a terminal obstacle clearance area, including an
  initial approach segment, a departure area, and a circling approach
  area, which would result in the vertical distance between any point on
  the object and an established minimum instrument flight altitude
  within that area or segment to be less than the required obstacle
  clearance.

Even though you are not directly in line with the runway you may be in conflict with a potential traffic pattern or approach segment.


Do horizontal stabilisers provide any lift? Do jumbo and smaller airliners' horizontal stabilizers provide any lift? Apart from maintaining the aircraft's angle of attack, can they perform the dual function that includes adding some lift as well? Are there any aircraft designs that use horizontal stabilizers for lift as well, apart from delta wing aircraft?

The horizontal stabilizer provides lift, but usually in the negative direction.
Could one provide positive lift?

The answer depends on cg location.

Forward CG, the answer is no.

Aft CG, the answer is yes but only if the CG was aft of the center of lift.

In other words, the more forward the CG is compared to the center of lift, the more downforce the tail must provide.  The lift from the horizontal stab in the "wrong direction" must be countered by the wing, and thus there is more induced drag.  For a given aircraft gross weight and thrust/power, there will be a higher cruise speed with a more aft CG.

There are practical limits to extreme fore and aft CG positions, and so each aircraft has an allowable "envelope" for loading for safety margin.

Aircraft are designed to have a range of allowable CG locations to make loading easier before the flight (especially for cargo aircraft), and also to allow for passengers & crew to move about the cabin in flight.

Horizontal stabilizers could be sized smaller but that would decrease loading flexibility, decrease passenger comfort, and decrease aircraft handling performance; often all airfoils and control surfaces are designed with many factors in mind, for good control harmony, good ride in rough air, for stability on instrument approaches, for flexible loadings of various belly and main deck cargo holds / passenger configurations, etc.

Flying wings and delta wing designs come to mind as aircraft without horizontal stabilizers, such as the Northrup Spirit or Convair Delta Dart.

Your other question, would manufacturers design horizontal stabilizers to provide lift?
Hopefully you can see by now this is not a design goal.  Wing design is so advanced that designers are making amazingly beautiful and high-performance wings that are most efficient at creating lift.  Look at a Gulfstream V wing or Boeing 747 wing.  It is not efficient to create a wing that doesn't work great and then needs an additional surface to help make more lift.  Exceptions to that might be bi-planes or tri-planes, as they used several shorter wings instead of 1 longer wing, but that is not practical in air transport.  How many Boeing Biplanes and Airbus Triplanes do you see traveling the globe? It's simply better to put all the lift needed into a single wing design.


Is pressure lower than ambient on the pressure (bottom) side of an airfoil? I've been reading about this for quite some time and thought I understood it. Then somewhere someone mentions that air under the wing has higher velocity than ambient thus a lower pressure than ambient. I couldn't find any other reference to this so here I am.

What this means is that, in a purely hypothetical situation, without the upper part of the wing generating a lower pressure zone the airplane would actually be pulled down because the pressure on top would be ambient thus higher pressure than the bottom.

This makes sense since hitting air molecules with the wings will cause them to accelerate and suddenly move faster than ambient, thus have lower pressure.

How accurate is this?

Picture version:

If the airfoil generates lift, pressure on the upper side has to be lower than on the bottom. Still, there can be suction (less pressure than ambient) on both sides.

For an extreme example, take the airfoil from US patent application 2004/0094659 A1 by Dan Somers. It tries to stabilize the boundary layer over the first 80% by creating an increasing suction over chord. The picture below is shamelessly copied from this application.

Ambient pressure is at a pressure coefficient c$_p$ of zero, and negative values denote suction, i.e. lower than ambient pressure.

All lift is generated by the highly cambered flap while the forward wing will only start to contribute lift once the angle of attack is increased from the current value of -2°. Note that airfoils for high subsonic speed show the same philosophy of a rooftop pressure distribution over their forward part with high rear loading. Such airfoils exhibit a high pitching moment and require a larger tail surface for stability, which blunts their advantage of low drag a bit. The plot below is taken from US patent 3,952,971 by Richard Whitcomb and shows just such a transsonic airfoil with a weak shock on its upper side.

This plot shows the speed difference ∆v compared to ambient, and again higher speeds which equal more suction are positive.

All those airfoils will develop a suction peak at the forward end of the upper surface and a corresponding pressure increase on the lower side once the angle of attack is increased. Now a Birnbaum-type pressure distribution will be added and at high angle of attack, this effect will dominate the pressure distribution and will ensure higher than ambient pressure on the lower side. This effect will be the more pronounced the thinner the airfoil is - a thick airfoil exhibits a stronger displacement effect which adds a little suction on both sides.

  hitting air molecules with the wings will cause them to accelerate

Not exactly hitting - it is air molecules flowing around the wing which will contribute a speed increase and hence a lower local pressure. This can best be seen by the pressure distribution around symmetrical airfoils at zero angle of attack. Note in the plot below that suction is on both sides and growing with airfoil thickness. Of course at that angle of attack those airfoils do not generate lift, but when an angle of attack is added, they will, and it will need a higher angle to push the bottom side of the thicker airfoil into the pressure region of negative c$_p$ values.

Inviscid pressure distribution of symmetrical NACA airfoils (picture source).

  Ambient pressure is higher than any wing pressure

Not quite: Note that all plots show a pressure peak at the nose and a pressure recovery to slight overpressure at the trailing edge. While most of the pressure around a thick airfoil at low angle of attack is indeed lower than ambient, the stagnation point will always ensure that this is not true for all of the airfoil.


Why paint a British roundel on a non-British Lynx? In recent years, some of the Westland Lynx helicopters of the Portuguese Navy have undergone some form of mid-life update (MLU) in order to have their engines and avionics upgraded. Also, allegedly, a few Portuguese naval aviators have undergone training and qualification on these updated Lynx helicopters.  Allegedly, such work took place at Leonardo's site in Yeovil, Somerset, England, United Kingdom.
Interestingly, articles on the aforementioned events do display photographs that show a British roundel alongside a Portuguese roundel on Lynx helicopters of the Portuguese Navy. The following photograph shall corroborate my claim.

Question
Why would one paint a British roundel on a non-British Lynx?
At the moment, only two hypotheses occur to me:

Though the aircraft being upgraded do belong to the Portuguese Navy, the test pilots are British.

If a trigger-happy fighter pilot in his pretty Typhoon passed by, he would know that the Portuguese Lynx is in British airspace with the permission of Her Majesty's Government and that Albion's oldest ally is not actually invading Old Blighty. Thus, it should not be shot down.

References
On Portuguese Lynx helicopters with British roundels:

Marinha Portuguesa, Helicóptero da Marinha Portuguesa realiza primeiro voo após processo de modernização, 18 de fevereiro de 2020. [Google's Portuguese-to-English translation]

First flight for upgraded Portuguese Lynx (2020)

Portuguese pilots in UK for Lynx Mk95A (2020)

On Brazilian Lynx helicopters with British roundels:

Leonardo: upgraded Brazilian Navy Super Lynx makes successful maiden flight (2017)

Third Wild Lynx for Brazilian Navy (2019)

Brazilian Navy completes Super Lynx Mk21B acceptance (2021)

Best guess; the photos are from the delivery flights in the 90s. The helicopter in the photo has the same registration as when it was first delivered (ZH583) and has not been active since.
Update: Although I'm having problems finding an authoritative source, it looks like the registration was resurrected for test flights post-upgrade. Mark Youd has taken a few photos of ZH583 recently(flickr), it was listed in the April update from a site called "Military Aircraft Markings" and looking at various planespotter forums and various flight tracking sites(1)(2) you can find multiple reports of flights being undertaken using the original ZH583 registration.
The roundel and registration is temporary and easy to remove, but was required for the test flights in the 90s as well as prior to delivery post-upgrade. Looking at other photos you'll see the Portuguese registration on the tail; on your photo this area appears to be covered up to avoid having an aircraft with two different visible registrations during test flights.
As for your hypothesis; the second is totally off target. There are loads of barriers in place to avoid having any situation involving a trigger-happy fighter pilot, such as predefined rules of engagement and procedures civilian and military control centers follow.
My guess is that the first one is closer to the truth; although I haven't found a source for it, I can imagine that it would be easier for the factory and the test pilots undertaking the upgrade and test flights to schedule and log flights using the UK registrations.


Why must a pilot enter "Upwind" when entering the traffic pattern for RWY 9 at Linden (LDJ) airport in New Jersey? The chart supplement procedures require aircraft to enter the traffic pattern "Upwind" for Runway 9 at Linden (LDJ) airport in New Jersey.

Question: Why is this required?

Chart Supplement:

New York Terminal Area Chart cutout showing Linden airport:
link to chart

Picture of "Upwind" leg from the Aeronautical Info Manual:

To keep aircraft away from the multiple obstructions to the east, and also not force people to make their approach from the direction of EWR and mitigate possible conflicts with traffic from that airport.


Why don't flights fly towards their landing approach path sooner? For example shown here, the flight is heading to the centre of the airport, until it gets close when it then moves into it's landing path. This is an inefficient use of time, fuel and emmissions, why can't the airport tell the aeroplane exactly which runway and direction it will land earlier so it can more efficiently head towards the approach.

In general, IFR flights through controlled airspace use airways (highways in the sky) to fly between waypoints. The particular flight you show looks like it arrived via the N774 airway to a waypoint MARLN:

(skyvector.com)
The traffic flow around busy airports like Kingsford Smith (YSSY) in Sydney is usually structured using Standard Instrument Departures (SIDs) and Standard Terminal Arrival Routes (STARs). Your example was probably on the MARLN5 RNAV STAR:

(from the Jeppesen chart for MARLN5 at YSSY)
From somewhere after the JAKLN waypoint, the air traffic controller (ATC) would have instructed the flight to turn right to intercept their final approach path (probably to runway 34R).
All of this structure (airways and procedures around busy airports) exists to allow for an efficient flow of traffic that can be easily managed by ATC. There are many things to consider when these paths are designed:

avoiding conflicts between aircraft (e.g. between departing and arriving aircraft or between flights from different airports in the area)
restricted airspace (e.g. airspace reserved for the military or avoiding flights near sensitive areas, like nuclear power plants)
noise abatement (especially near large cities you want to avoid overflying the city center at low altitudes)
terrain (not really relevant for Sydney)

Nonetheless, one can deviate from these fixed routes. ATC might clear an aircraft on a more direct route if traffic and restricted airspace allows this (very common right now due to the pandemic). Some countries have even removed all high altitude airways and replaced it with Free Route Airspace.
The problem with setting an aircraft on a direct route for final approach interception is that this would have to be done far away from the airport. The aircraft needs time to descend and slow down (usually more than 100 NM). At this point they are typically not handled by the approach controller for the airport they are landing at, but still by the Area Control Center (ACC). This would require significantly more coordination between various controllers and is probably not very efficient in busy airspace. During the current pandemic with significantly less traffic, you might see it though.


Why am I getting unusually high CHT on ground operations on one engine in a Seneca II? Aircraft had sat for 3 months, and on startup the right engine CHT (Cylinder Head Temperature) was climbing noticeably higher than the left. After taxiing and run up CHT was near top of green. Redline is 460. Other engine readings are normal. Annual inspection completed, mechanic said compression is ok and CHT still in green. I had the probe changed, but the problem persists. During flight, the reading was quite high compared to left engine and compared to what it used to be. What could be the reason for this?

If the gauges are good (swap them to see if the problem moves to the other engine), the baffling is good (baffles must be tight to the fins to force air between them with no leaks around the plenum), the cowl flap works normally (not being unknowingly blown partly closed by loose linkage), the most likely cause is an intake leak that's causing the cyl with the probe to run lean.
Either the rubber intake hose is bad, the gasket at the cylinder is leaking, or the sheet metal intake tube to which the hose connects, that is swaged into the intake spider tubes at the oil sump, is leaking.
This is an old problem on Lycomings. The little sheet metal pipe stub  is installed with a rolled bead that engages with a female groove in the hole in the sump, and depends on interference for a seal.  They can lose the interference and start to leak (you will be able to move it if you loosen the rubber hose).  There is a (very expensive) swaging tool (I believe you can rent from Lycoming) that re-rolls the bead from the inside.  Some people prefer to just remove the sump and send it somewhere to be done.
Although the redline is there, you really want to keep CHTs below 400F if at all possible.


If skydivers cannot jump on a flight, what should I take care of when landing? Piloting an aircraft, if skydivers cannot jump on a flight, what should I take care of when landing?

Are there any special recommendations which should be taken into account?

You should descend in a controlled way, taking into account that your descent rate should be ≤ 29 mph (less than 13 m/s), once below 2,500 feet.

If the descent rate is higher than that, then there is a risk of the AAD popping the skydiver's reserve parachute, mid-flight.


How does a wing mounted jet engine on a supersonic airplane prevent the interference in the flow due to Shock? Wing mounted jet engines face the free stream at Mach number 1 or above, and they work perfectly for Mach numbers below 1 as well, even though the free stream characteristics change a lot after Mach 1.

How do the engines manage to work despite the fact that after Mach 1, the Shock waves would try and disrupt the normal airflow?
If the engines are optimized to work at above Mach 1, does this cause any trouble for them to work under subsonic conditions?

Don't confuse with "Why cant jet engines work with supersonic flow?"

Flow conditions are not so different, only the reaction of the flow to an obstacle is. By shaping the intake appropriately, supersonic flow is handled easily, and shocks will be helpful in decelerating and compressing the flow.

However, supersonic flow demands sharp intake lips which are hit by the flow at the right angle, otherwise drag rises quickly to intolerable levels. These sharp lips will cause flow separation in subsonic flow when hit by the flow at an angle, so aerodynamic tricks like bypass doors need to be added to the intake to keep flow angles at the intake lips in check.

Note that the intake will ensure a flow speed around Mach 0.5 at the compressor face of the engine, regardless of flight speed. Therefore, the engine will not need to be optimized for supersonic flight. However, to keep its frontal area low and the nozzle speed high, its bypass ratio should be low. The only troubles this causes are increased engine fuel consumption and noise.


What has been the maximum number of failed landing attempts for any commercial flight yet? Top DGCA officials say they do not recall any other instance of this kind where a plane tried to land unsuccessfully six times and then finally touched down in the seventh attempt — whether in India or abroad. (Source)

A better written report of the incident.

Coming to the question, what has been the maximum number of failed landing attempts for any fully loaded commercial airliner?

As far as I know, nobody actually maintains a register of go around. A go around is not a failure, nor a fault.

However each missed approach reduces the fuel quantity which may become insufficient. The crew will not continue to try to land at the same airport if the likelihood of better conditions at the alternate airport are high.


Is it possible for a Citation Jet not to have an APU or AIR COND? In reviewing a number of CESCOM10 reports it has become apparent that some of the aircraft don't report APU hours (instead they report AIR COND).

Is it possible that a Citation Jet doesn't have an APU?

For those reports that do report APU hours, no AIR COND hours are reported ... is it possible that there are Citation Jets that have APUs and no AIR CONDs?

It is possible for a Citation jet to not have an APU, two of them that come to mind are the CJ2 and CJ3 aircraft. An aircraft with an APU can have an independent air conditioning system or not, it just depends on the installation and manufacturer. Some airframe manufacturers use engine (or APU) bleed air to condition the cabin air temperature. Something like an APU would have overhaul limits similar to an engine, propeller, or a combustion heater like in smaller aircraft. Anything with a life limit would have to be tracked, so that could be individual components of a larger system, such as the starter/generator of an APU, or a compressor motor of an air conditioning system. I think what you're seeing is a coincidence.


What additional aircraft equipment is required to fly a US registered airplane in Europe? If I want to take an airplane to Europe, what additional aircraft equipment is required beyond the US requirements?

For instance, I know that we need 8.33Khz spacing radios, what else is there?

Also, I heard that it will be changing in 2015 to have additional requirements.  What will those be, and will there be any exceptions (ie, can we obtain a waiver)?

An overview of ATC related avionics can be found on the Eurocontrol website. There are a couple of things changing in 2015.

The list below includes change to ATC related avionics requirements in 2015.

In addition other avionic requirements not related to ATC are imposed, but that is outside my field of expertise.

Surveillance

Commission Implementing Rule (IR) (EU) No 1207/2011

Commission Implementing Rule (IR) (EU) No 1028/2014 (Amendment of 1207/2011)

ADS-B

ADS-B (1090ES) will be mandated  from 7 January 2017 for aircraft with MTOM > 5700 kg and Max cruise TAS > 250 Kts with an individual  certificate  of  airworthiness  first  issued on or after 8 June 2016. For aircraft certified before 8 June 2016 with the same MTOM and max cruise speed class ADS-B will be mandated after 7 June 2020 .

Applies to all IFR flights in the European Civil Aviation Conference (ECAC) airspace, excluding oversea territories.

Mode-S Elementary Surveillance (ELS)

Mode S ELS will be mandated for all aircraft operating according to Instrument Flight Rules from 8 January 2015

Applies to all IFR flights in the ECAC airspace, excluding oversea territories.

Mode-S Enhanced Surveillance (EHS)

Mode S EHS will be mandated for new aircraft with MTOM > 5700 kg and Max cruise TAS > 250 Kts from 8 January 2015. For existing aircraft in the same MTOM and max cruise speed class Mode S EHS will be mandated after 7 December 2017.

Applies to all IFR flights in the ECAC airspace, excluding oversea territories.

Communication

Commission Implementing Rule (IR)(EU) No 29/2009

Controller-Pilot Data Link Communications (CPDLC)

CPDLC (VDL Mode 2) is mandated above FL285 from 5 February 2015

Applies to all IFR flights in the ECAC airspace, excluding oversea territories.

Safety Enhancements

Commission Implementing Rule (IR) (EU) No 1332/2011

TCAS

From 1 December 2015 TCAS II version 7.1  will be mandated for all aircraft build before March 2012 with MTOM > 5700 kg and Max cruise TAS > 250 Kts operating in EU airspace. Aircraft first certified after 1 March 2012 already need to operate with TCAS II version 7.1.

Outside EU airspace, but within ECAC airspace, TCAS version 7.0 is still allowed.


Why does Canada recommend a minimum rate of climb for ultralights of 300 ft/min? What is a safe minimum rate of climb for ultralights? I understand most ultralights climb at least 300-800 ft/min and in fact the Canadian ultralight specs recommend a minimum rate of climb of 300 ft/min. Even the Lazair's specs note a rate of climb of 400 ft/min.

Why does Canada recommend 300 ft/min specifically? Why not 120 ft/min?  60 ft/min? Even at 60 ft/min, you could clear a 4' fence in 4 seconds. Of course you would want some clearance, so say 20 seconds. Seems pretty good in my book. Need to clear 50' trees? Just kite around in a circle.

When you fly gliders you discover it's quite common to run into air that's descending at 1-200 fpm, or "sink" in soaring-talk.  Descending air next to a thermal, or air descending due to downsloping terrain.  It's a lot more than that at times, but a couple hundred fpm is typical.

On a day where there's any convection (with rising air, there is always equivalent descending air adjacent to it) you are in sink quite a lot.  A 300 fpm ROC provides a reasonable assurance that you will be still able to climb while in most (but certainly not all) conditions of descending air, barely.

If you have an ultralight that can only climb 100 fpm, this might be fine on a smooth day with stable air, if you're patient.  If there is any vertical motion in the air however, you have a problem.  The minimum climb rate requirement is an attempt by the regulator to ensure that that average ultralight buyer will have a machine that won't kill him because it couldn't even out-climb a bit of subsiding air at the end of the runway.


What's usually going on in a "hot" military operations area (in the US)? Like many people in aviation, I've been around pilots who've flown in or through the edge of a Military Operations Area (MOA) while operating under visual flight rules. Usually they ask ATC if the MOA is hot, and sometimes the answer actually is "yes".  In that case, the pilots stay clear for safety.  My question is, what's usually going on in the MOA at the time and how bad would it be to enter it in VFR?

There are few reputable sources on what typical operations are in military operating areas.  This Global Air blog is the best explanation I could find, although this post isn't a bad source.  Those sources seem to err on the side of exaggerated caution though, describing "lights off" operations, practice dogfights, and 500 KIAS speeds.  Are those kinds of operations daily, or evenly weekly, occurences in military operating areas?  Where on the spectrum from the mundane "practicing approaches" to dangerous "simulated high speed dogfight operating heads-down" do most military flights lie? Are operations consistent or do they vary from place to place and month to month?

Background information for those outside the US:  MOA's are defined in the Aeronautical Information Manual (AIM), paragraph 3-4-5, as well defined airspaces near military bases "for the purpose of separating certain military training activities from IFR traffic."  They are different from restricted zones with particular defensive significance or bomb and missile activity.

Military pilot here.

I can certainly understand why there's confusion surrounding MOA's, having been a Private Pilot long before I flew for the military, and I'm glad you asked the question.

The second post you referenced is exactly right. It is extremely common (at least in our training areas) to have  dogfighting and other tactical training with airspeeds above 500 KCAS, and altitude changes of thousands of feet in seconds. No one uses a MOA for instrument approaches. This type of flying occurs multiple times per day, and it's extremely frustrating when civilian aircraft fly through the airspace without talking to ATC. We generally don't have a lot of time to work in the area, so we have to maximize the training we get. Stopping a fight/intercept/practice bomb run because a Cessna wanted to transit the airspace generally results in a reset of the entire scenario and wastes countless dollars and training opportunities.

If there's an emergency we will, of course, understand and please do whatever keeps you safe. Short of that, please, please get flight following, and do not fly through a MOA.


Can an airfoil have multiple aerodynamic centers? Aerodynamic center is a point where the moment is independent of angle of attack. Can we have 2 or more such points? Does it necessarily lie inside the airfoil?

No, it's not possible to have them simultaneously. Here's a proof by contradiction:
Assume that there are two points on the airfoil that have constant pitching moment, located at $x_0$ and $x_1$, each having constant moments $M_0$ and $M_1$, respectively, and that $\frac{\partial{M_0}}{{\partial\alpha}}=\frac{\partial{M_1}}{{\partial\alpha}}=0$ (which make them aerodynamic centres).
Therefore, using the $M_0$, we can write the moment about any other point as:
$$M(x)=M_0 + L(x-x_0) \tag{1}$$
where $L$ is lift and is a function of the AOA, $\alpha$.
Using (1), we can try to calculate the moment at $x_1$, which gives:
$$M_1 = M(x_1)=M_0+L(x_1-x_0) \tag{2}$$
Differentiate (2) with respect to $\alpha$, and we get:
$$\frac{\partial M_1}{\partial \alpha} = \frac{\partial L}{\partial \alpha}(x_1 - x_0) \tag{3}$$
But (3) can't be zero since $\frac{\partial L}{\partial \alpha}$ is always non-zero, which contradicts with the assumption that $\frac{\partial M_1}{\partial \alpha}=0$.
However, if the lift is non-linear, then the AC will move around at different AOAs, each satisfying local linearity of the aerodynamic center definition.