Can a person be operating an aircraft in a "Careless" and "Reckless" manner at the same time? Or are these two different standards? U.S. 14 CFR Part 91.13 Careless or reckless operation states:

(a) Aircraft operations for the purpose of air navigation. No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another.

Can a person be operating contrary to this regulation in both a "Careless" AND "Reckless" manner during the same operation or are these two separate offenses under single FAR (91.13 [a])?
This is an interesting article that discusses Is “Careless” Different From “Reckless” Under FAR 91.13(a)?
My question is certainly not, in general, a novel one. Maybe there is a knowledgeable person in the ASE community that can shed some light on this question.

After reading the comments and responses below (as of 5/11/2021), I have added some editorial information to my question: (probably far more than you want to read, but interesting nevertheless)
This link from SMU (Southern Methodist University, Dallas, TX), entitled A Legal Analysis of 14 C.F.R. Part 91 See and Avoid Rules to Identify Provisions Focused on Pilot Responsibilities to See and Avoid in the National Airspace System (2015) provides some historical context regarding the evolution of FAR 91.13 (and its predecessor regulations).
It's a long read, but importantly, beginning on page 71 is a background and analysis of 91.13.  Additionally, on page 81 para. 4, entitled "Reckless Standards," is an interesting discussion closely on point with my question (above).
Also, on page 84, para. c., discussing a case regarding a violation of FAR 91.155, "The administrative law judge (ALJ) and the Board  uniformly characterized this..." (the actions of the pilot involved) "...as "intentional, reckless and deliberate behavior and prohibited the application of the Aviation Safety Reporting Program." (emphasis is mine)
It should be noted that in  AC 00-46 (Aviation Safety Reporting Program - filing of a NASA Aviation Safety Report) no civil penalty or certificate suspension is imposed if the criteria for inclusion in the program are satisfied. However, one of the eligibility requirements for receiving the benefits of filing a NASA form is that the "violation was inadvertent and not deliberate." (see para. 12.3.1 in AC 00-46)
So, in the case mentioned in the SMU analysis (above) the ALJ and NTSB found the behavior of the pilot "reckless" and "deliberate" and, apparently on this basis denied benefits otherwise available when filing a NASA form under the Aviation Safety Reporting Program.
With all of the great responses and commentary taken together, there seems to be convincing information that 91.13 specifically provides for, but does not mandate, a distinction to be made between a "careless" operation and a "reckless" operation.

From a legal perspective, 'careless' and 'reckless' sound similar but are quite different.
Careless is the antonym of prudent and careful. There is usually no attempt to analyze the state of mind of the offender (other than in defense to reduce a more serious charge to the less serious careless.)
An example might be failing to lower the landing gear because the pilot forgot -- this would very likely fit the definition of careless. Careless is usually not a criminal violation in American legal frameworks (such as careless driving) but may be when combined with a statute violation.
Careless is also used as a description of the violation of the standard of care that is a reasonable expectation of care from those acting in a professional capacity or while subjecting others to danger or under a common carrier standard of care. The FAA use of careless is purposely ambiguous to allow any fitting definition to be used.
Reckless involves the wanton or willful disregard of other people's safety and/or property. It is usually a crime. Flying under a bridge or buzzing your buddies house would likely fit the definition of reckless. The burden of proof is on the prosecution to prove that state of mind of the defendant. HERE is a legal definition. HERE is the FAA's regulatory definition of what the FAA/ NTSB consider reckless.
Negligent would usually be considered between Careless and Reckless in severity and is usually the lowest level of criminal culpability. (Recall that FBI Director Comey's conclusion about Secretary Clinton's private email server rested on his definition of gross negligence vs extremely careless. The first is a crime with classified material; the second is not.)
The FAA likely uses Careless or Reckless in §91.13 to lower the bar that neither is tolerated and the difference between them will be dealt with in administration and penalties. It is a broad catch-all that includes negligent. If you go to the NTSB database of infractions, 91.13 is the most common. It is usually an add-on or derivative charge allowing for emergency revocation of a pilot's certificate. The applicable difference between the ALJ applying careless as opposed to reckless is the degree of penalty (license suspension vs license revocation) and, as you pointed out, whether the ARSP exemption to penalties apply.
Some examples of 91.13(a)claims; some of which parse through the difference of careless and reckless:

A pilot forgot to remove the nose-wheel chock of a propeller aircraft. He asked his wife to remove the chock from the aircraft with the engine running. She was fatally injured. CASE

Pilot wrongly declared a minimum fuel condition to ATC. CASE

'Buzzing' twice over a nude beach with a pilot on the beach as a witness. CASE

Misunderstood ATC clearance causes breach of separation. CASE

Helicopter pilot having sex with a passenger recorded on video. Martz case and ARTICLE

The Martz decision combined with the FAA definition of reckless can be derived into a standard of conduct that will likely ground you.
Under Martz, and previous cases, the standard of a finding careless or reckless is:

Regardless, as we have previously held, the Administrator need not
establish actual danger, a flight suddenly in peril, in order to
prevail in proving that a respondent has operated an aircraft in a
careless or reckless manner. In Administrator v. Lorenz, NTSB Order
No. EA-5205 at 2-3 (2006), we recognized that a showing of potential
endangerment is sufficient to prove a violation of § 91.13(a), and
cited several cases holding that proof of actual danger is unnecessary
for a § 91.13(a) charge.

And the relevant FAA standard is:

The inspector can infer a deliberate and willful disregard of the regulations or safety standards from the circumstances surrounding a violation. [omited text]
While there is no regulatory definition of the term, “reckless,” it
has been defined in cases decided by the NTSB. A reckless operation
results from the operation of an aircraft conducted with a deliberate
or willful disregard of the regulations or accepted standards of
safety so as to endanger the life or property of another either
potentially or actually. Accordingly, any such reckless behavior
violates § 91.13.

So potential of danger (not actual danger) that with a state of mind that can be inferred from the circumstances (not actual mens rea) is the applicable standard under § 91.13.
An excellent history of the development of 91.13 can be found HERE starting on p. 71 of the PDF.
Also keep in mind that the FAA is only dealing with administrative penalties; if you do something considered reckless there may be additional federal, local, or international criminal penalties as well as civil liability.
So to answer your question of Can a person be operating an aircraft in a “Careless” and “Reckless” manner at the same time? Or are these two different standards?
Since the spread between careless on the one hand and reckless on the other is large, one infraction is unlikely to be both simultaneously1. It is really more of an ambiguous spectrum of stupid and careless on the one extreme, to reckless and perhaps homicidal on the other extreme, with everything-we-don't-like in between. The difference between the two is largely the degree of the offense and the inferred state of mind of the offender.2

1 It very possible that an initial offense would be considered careless (such as forgetting to remove the nose chock) but the pilot's reaction is then judged to be reckless (sending his wife to remove the chock with a running engine resulting in her death.)
2Administrative legal procedures, such as FAA or NTSB enforcement actions, have significantly reduced burden of proof compared to criminal actions. See the FAA standard that allows intent to be inferred from the circumstances of the violation. See FSIM § 8900.1 CHG 422 14-3-5-1


What is an Inertial Navigation System? How does it work? In this question, the answer notes that some ADS-B systems are connected to Inertial Navigation Systems (INS), and says they are less accurate than GPS.  What exactly is an INS?

A couple sub questions:

Why is it less accurate?
The other post mentions they tend to
develop biases as they get older, why is that?
Are they being phased
out?  Or are they used as backup?

Inertial Navigation Systems, unlike other navigation systems, do not depend on external (radio) measurements. Instead an INS keeps track of its position by accurately measuring acceleration (accelerometers) and rotation (gyroscopes). It therefore works in remote areas where there are no ground based navaids available.

Initially, the INS gets its position from pilot input at the gate, or in more recent systems from GPS, sometimes even during flight. By measuring all the accelerations and rotations and integrating them into speed and direction the position is tracked. In doing this, the INS has to correct for the rotation of the earth and the related Coriolis force.

Due to small inaccuracies in the measurements the velocity error and, with that, the position errors grow over time.

Wikipedia has quite a detailed article about the history and working of the INS.

While raw INS position has mainly been replaced by GPS measurements on oceanic flights, the system is not being phased out. GPS is a sensitive systems and by crosschecking it with INS, errors can be detected in both systems. It is often used as a backup to GPS.

Integrated GPS / INS systems provide better systems integrity and allow the navigation system to coast through short GPS outages with high accuracies. In addition to that, the (laser) gyroscopes of the INS are often used to provide data to the digital artificial horizon displays in the cockpit and to the auto flight systems. In this case the term Inertial Reference Unit (IRU) is used, which acts as a basis for the INS.


At what distance from magnetic north do pilots start referencing true north for heading? The Earth's magnetic poles are constantly shifting, resulting in a significant distance between the true and magnetic poles. This means that while using them as references for heading at lower latitudes makes sense, using them as such while flying in polar regions causes often unacceptable inaccuracy.

In a simulator, I noticed that many modern airliners have a toggle to switch between referencing true and magnetic north as appropriate; but at what distance from a pole would this toggle be activated?

In Boeing aircraft the default is to select MAG. When the aircraft enters the polar region it will auto switch to TRU. The pilot can also select TRU when outside the polar region.

The polar region is defined as north of 82 deg N latitude or south of 82 deg S latitude. It also includes the region north of 70 deg N between 80 deg W longitude and 130 deg W longitude and the region south of 60 deg S between 120 deg E and 160 deg E longitude.


How do turbofan internals handle the load from the thrust? To my understanding, turbofan engines get the majority of their thrust from the fan in front of the engine, up to around 70-80% while the core flow generates around 20-30%.

Forward movement is achieved by utilizing Newtons 3rd law - by moving masses of air backwards and thereby moving the aircraft forward.

The thrust will first push the engine forward, and then the engine mounting, and then the wing and the aircraft as a whole - but how exactly is the load from the fast moving thrust air taken up by the engine internals?

As wings generate lift, they bend to a varying degree. Do the fan and engine internals, e.g compressor and turbine blades bend as well? I can imagine the fan taking up a tremendous amount of thrust load and wants to leave the engine and travel forward out the housing.

How much of this is true? Any input or suggested reading on this is highly appreciated!

The thrust is generated at the fan and compressor blades, as these are the components which push the air back. It is then carried through their attachment disks to the shafts and from there to what are called thrust bearings. A simple thrust bearing is a fixed flange against which the shaft pushes, but of course they are usually a lot more sophisticated. Thrust can also be generated by careful shaping of the core exhaust duct, but on a subsonic turbofan it can at best be only a small amount. The force is then transferred through the engine's structural framework to its mountings and thence to the airframe itself.

Yes, everything in the engine will deform a bit under load. Luckily the load paths tend to be short, but it still has to be made stiff and strong, with as you say the mounting carrying the full thrust. Extensive use of high-strength materials is made in the engine to keep deformation down to manageable levels. Varying amounts of thermal expansion of different parts also take place. These combined movements necessitate the designing-in of mechanical tolerances, to prevent the binding of moving parts or local build-up of mechanical stresses.


How does turbine efficiency compare with internal combustion engines if all the turbine power is converted to mechanical energy? It is widely know that early turbojets guzzled fuel and created thrust simply by spewing accelerated matter out the back.  Modern jets have come a long way in earning a better reputation with efficiency improvements.

If an aircraft mounted the exact same propeller on a supercharged piston engine and a turbine, and flew under identical conditions at the same pitch and rpm, how much more fuel would the turbine use (possibly including weight savings benefits for extra credit).

I am picturing a two engined aircraft with the two types of engines flying side by side at around 350 knots.

The most efficient IC engines are large Diesels. At the extreme end are ship engines with better than 50% thermal efficiency resulting in a specific fuel consumption of only 0.260 lbs/hp/hour or 158 g/kW-h. But even supercharged truck diesels achieve above 40% thermal efficiency at high load (this NHTSA study gives 42%).

Aerodiesels have achieved 220 g/kW-h already with the Jumo 204 and 205 of the early 1930s. Even the modern Thielert diesels (now sold by Continental) are hardly better, claiming 214 g/kW-h. Also the Napier Nomad, a super- and turbocharged aero diesel with utmost efficiency as its design goal just reached 219 g/kW-h.

Gasoline engines start at about 240 g/kW-h; this value is achieved by the Lycoming IO-390 with fuel injection. Without fuel injection, specific consumption rises to 260 - 280 g/kW-h which is typical for a Lycoming O-360 at 65% power. Note that the Jumo 213, one of the more efficient WW II-era piston engines, already achieved 260 g/kW-h even with 87 octane fuel and a compression ratio of only 6.93:1 at its most favourable operating point. Advanced Innovative Engineering, who have taken over the Norton-Wankel engine, claim 310-350 g/kW-h for their 650CS with 120  PS.

Comparing that with turboprops needs some conversion of thrust into power. This is only valid for a specific flight speed. If you do that at cruise speed, the large turboprops Progress D27 and Europrop TP400 claim a consumption of around 240 g/kW-h. Smaller turboprops rarely achieve below 300 g/kW-h.

To save you from the trouble of looking up and converting the data in the last link, here is a selected list:

Allison 250 $\;\;\;\;\;\;\;$: 370 g/kW-h. This is a typical small helicopter engine.
Garrett TPE331$\;\;$ : 310 g/kW-h. This is used on small turboprops like the Do-228 or the Merlin III.
PWC 126A $\;\;\;\;\;\;\;$: 280 g/kW-h. Getting larger - BAe ATP.
Rolls-Royce Tyne : 237 g/kW-h. This has long been the largest turboprop in the West and used on aircraft like the Canadair 400 / CL-44.

Please note that those turboprops feed on kerosene while the piston engines need gasoline. But by basing the comparison on a per-mass basis, it is valid because the energy densities of both are almost identical. Very large turboprops are as efficient as gasoline piston engines, but diesels still have a small advantage.

Now for turbofans. Here we have thrust which needs to be converted into power first by multiplying it with flight speed. It would be nonsensical to compare the static case – here by definition turbofans do not produce power. For the nitpickers: Yes, I need to look at the gas speeds ahead and behind the engine, but still, this makes for a poor comparison: Most static values are from test stands with all accessories removed and no losses for engine mounts and fairings. I will instead use the figures in cruise given in this answer, using a fuel burn of $b_f$ = 18 g/kNs and a speed of Mach 0.78, which equates to a flight speed of 262 m/s in 11.000 m altitude. Multiply by 3600 for a per-hour value and divide by 262 (the N are in the denominator!) and you arrive at 247 g/kW-h. So again, very similar to good gasoline piston engines but not as good as diesels.

But again this comparison has to be taken with the proverbial grain of salt. Now we need to have a closer look at speed. Thrust-specific consumption goes up with speed and roughly doubles between the static case and cruise speed for a modern turbofan. The GE-90 achieves 8 g/kN-s static and 15 g/kN-s at Mach 0.8 – that would be just 209 g/kW-h and be on a par with the best diesels. For comparison: The installed figures for modern military engines in supersonic aircraft are 20 g/kN-s. And regarding the fuel-hungry turbojets: The old Jumo 004 achieved 39 g/kN-s – just twice as much with a compression ratio of only 3.3:1. Real fuel guzzlers were the Argus 014 of the V-1 with 107 g/kN-s in cruise.

While turbine engines gain in efficiency with altitude due to colder intake air, the diagram below comparing the Jumo 213 A with the J version (source) shows an increase in power specific fuel consumption with altitude. Note that flight speed will also rise with altitude and is not given, so I suspect this is more due to higher speed than higher altitude. Again, these are real-world data from flight test with the engine installed in a FW-190D (source). Going from sea level to 10 km which roughly doubles true air speed raises the specific consumption by 20%.

Comparison chart between Jumo 213 A and J. Flight altitude is given in [km] along the x axis and specific consumption along the right y-axis. Multiply by 1.34 for g/kW-h. The lower set of lines are for partial load operation between 2100 and 2700 RPM (A version) rsp. 3000 RPM (J version) while the upper set of consumption lines are for maximum power operation at 3000 RPM (A version) rsp. 3400 to 3700 RPM (J version), partially with water-methanol injection.


If we add a video recorder in the cockpit to complete FDR/CVR, will we add a blackbox? The introduction of a video recorder in addition to the current audio and flights parameters recorders used for crash investigation (CVR and FDR) is suggested by this article (published in the New York Times in 2004) citing officials of the National Transportation Safety Board, and called image recorder in a most wanted list (published in 2012) of the FAA.
Those two references shows the introduction of a video recorder is taken seriously. I don't want to debate whether this is usefull neither what should be recorded (wide angle of the whole cockpit, close view of switches and screens, black & white or color, ...).

Given the answers of this questions, the video track record's requirements should be very close to the one of the CVR, thus adding this track to the CVR seems reasonable.

If we add this video track to all tracks recorded by blackboxes, will this records to an existing blackbox (either the FDR or the CVR) or will we create a dedicated blackbox (resulting in three blackboxes)?

related questions :

Why could increases in cockpit voice and image recording potentially raise privacy concerns?
Why doesn't the black box also record video?

Before answering, let's look at these terms:

FDR - Flight Data Recorder

FDRs record all flight data, every button pressed, every control input etc. They record throughout the duration of the flight.

CVR - Cockpit Voice Recorder

CVRs record all voice communications through the radios and the chat pilots have between themselves. They record only the last 30-120 minutes.

So what benefit will adding a camera bring?

After an accident (God forbid) the investigators are not interested to see what was the color of pilot's shirt or was he picking his nose before he pressed a button. In addition, you would need several cameras to record every single action of the pilots, and even then it would be hard to figure out as some buttons are placed very close to each other.

FDRs solve this problem as any input from the pilots are recorded. CVRs capture all communications so the motive or reason behind any input from pilots are be found out.

I suggest you to read some NSTB investigation reports (here or here) to get a detailed idea how in-depth knowledge the investigators can get by these two instruments.


Does slipping in turns allow higher climb rates? Sailplanes, among others, use a cotton string to show the sideslip angle. I've often heard that while circling in thermals the cotton string should show a slight slip angle to climb faster. This effect can be observed specially at high bank angles with heavy, high span gliders like the ASH-25. The german skid Wikipedia-article has even a subsection about it; however, without references. Flying like this has also the advantage of lessening the stall risk of the inner wing.

Is the indicated sideslip angle of the cotton string real or only apparent and due to the uneven incident airflow? Has this effect ever been scientifically measured and is it used in larger airplanes with FBW and sideslip angle sensors while turning?

Source: Wikipedia.

Origin of the theory

Klaus Holighaus, one of the famous glider pilots of the 70s, and himself a glider designer at Schempp-Hirth, is at the origin of a controversy when he recommended not to turn with the ball centered, and especially when climbing in thermals. Mr Holighaus did see two problems with the perfectly coordinated turn:

It doesn't reduce drag as in straight flight.
It reduces the aircraft margin for roll stability.

I'm not an expert in the field, so I'll just rely on the article by Richard H. Johnson published in Soaring Magazine and titled "Do you really want to keep the yaw string centered?"

Before going into Klaus Holighaus' theory, let have a look at lateral stability.

Roll stability: Dihedral angle

Unless you want a very agile aircraft, an aircraft must have positive stability on the three axis, i.e. if the aircraft straight and level attitude is unsettled by some event, the aircraft must have a built-in tendency to cancel the effect of the perturbation and to return to its initial attitude.

Roll stability is required to prevent the roll angle to increase automatically after a small unwanted roll input by the pilot or by a cross wind gust. The aircraft must return to a null roll angle automatically to prevent nasty consequences, including entering a spiraling descent.

Roll stability is mostly provided by the dihedral angle of the wing as explained in How does the dihedral angle work? In short: The dihedral angle uses the sideslip to create an opposite roll motion.

No sideslip: No dihedral effect

We know turning is not controlled by the rudder but by rolling the wing with the ailerons. But at some point the lowered wing aileron may also be deflected downward for turn rate control, and this deflection may happen to be excessive:

  When  the  lowered wing's  aileron  is  deflected downward,  not only
  is  its  lift increased,  but also  its drag is  increased, and a
  skidding turn  will  be induced.

At the same time the lowered wing, being closer to the turn center, is flying slower than the raised one. Slow speed, high angle of attack and more drag for the aileron can induce a stall: If the lowered wing or its aileron stall, drag on this side is increased and the aircraft is likely to enter a dangerous spiral.

However in most of the cases we can stop skidding:

  The skid can  easily be corrected for by adding some top rudder to
  keep  the  skid  ball  centered.

The solution implies to add drag to the rudder, which is not satisfactory from a performance perspective.

Get the best of both worlds

This is where the mild-slipping turn theory comes from: By turning with a slight slip instead of a perfectly coordinated turn:

We keep the dihedral benefit to stabilize the aircraft around the roll axis. This is safer.
The negative roll moment provided by the dihedral allows us to use less ailerons deflection, so less drag and more speed, and better climb in the thermal.
We use less rudder, so even less drag, and even better climb.

The article's author adds this explanation about improving lift with the sideslip:

  Why slipping improves the climb in some gliders is not well
  understood. In generating lift, wings also generate spanwise flow,
  outward along the bottom and inward along the top of the wings. It is
  possible that there is flow separation near the tip of some circling
  sailplanes, and that slipping changes the spanwise flow enough to
  eliminate or reduce this. Separation can increase the drag
  significantly long before the tip actually stalls.

The article also enter in the details of why this is different when winglets are used on the wing. Slipping may induce a stall instead.

How much sideslip?

  The optimum degree of sideslip depends to some degree on both the
  sailplane's wingspan and dihedral angle. After many hours of flying my
  16.6 meter ventus a and similar sailplanes, I find that my best overall
  circling performance and handling characteristics occur while
  the canopy mounted yaw string is deflected about 10 degrees on the
  high side of the turn (a gentle sideslip actually).

Yaw string vs ball

The yaw string is also more accurately named the slip/skid string, as it doesn't indicates a yaw angle but a quantity of skidding/slipping, like the ball.

As @ymb1 commented, the string being on the canopy, ahead of the CG, its indication is exaggerated.

In a coordinated turn, the ball of the slip/skid ball indicator will be centered while the yaw string will be already indicating a slight amount of slip. This error will be magnified with actual slip.

The author estimates the actual degree of slip in his case is more accurately about half the indication of the string. See also Peter Kämpf's comment: "exaggeration is also caused by the fuselage shape [...]".


How can the pilot tell the center engine failed on a piston aircraft with three engines? There are a few aircraft, such as the Britten-Norman Trislander, that use three piston engines -- one on each wing and one mounted along the centerline somewhere.

This is fine and good, but how do you tell in a timely fashion that the #2 (centerline) engine has quit?  The engine gauges are in no hurry to tell you, as per Randy Sohn's Warbird Notes #6, and there's no adverse yaw because it's a centerline-mounted engine, but you still need to know and quick because unless you can get that prop feathered, there's a giant drag bucket hanging off your vertical tail!

If the engine quits you will lose some thrust which will affect the plane's handling. You may even begin to descend slowly which the pilot will notice.

Most importantly you have engine instruments which will tell you, quite quickly, the engine has quit. If you have one, your manifold pressure will drop since you are no longer producing power, or your tach will reflect what is happening.

If all that fails you I would think there would be an audible difference if the engine cut out.

This is the cockpit of the aircraft in question:

(Image Source: Jetphotos.net)

It does show independent MAP and RPM gauges for each engine as opposed to some planes that have a single gauge with multiple hands (one for each engine). You would surely be able to see an altered reading on one of these gauges.


Is the well known textbook-formula for net-thrust oversimplified or do I have a misinterpretation? In order to understand how Jet-Engines works I came across the "famous" formula for net-thrust:
https://en.wikipedia.org/wiki/Turbojet#Net_thrust
$F_{thrust} = Q_{out} \cdot v_{out} - Q_{in}\cdot v_{in}$
From well known physical law about momentum this sound quite reasonable for me.
But now assume an empty cylindrical chamber with nozzle at the end, mounted statically in a wind channel:

Regardless of any details, just by continuity equation we must have
$Q_{out} = Q_{in}$
and
$v_{out} \gt v_{in}$
Nevertheless, this construction would not produce a net propulsion in left direction. It it were true, we just had to put this "empty" construction on a plane...
I was thinking over that quite a time and become already a little crazy.
Where is my mistake? Or is the formula above not the whole truth?
Anyway, I'm not sure if
$v_{in} = v_{air}$
although it sounds reasonably for me.
But even when I take the formula
$F_{thrust} = Q_{out} \cdot v_{out} - Q_{in}\cdot v_{air}$
a left thrust would be produced, whenever
$v_{out} \ge v_{air}$
Is this the key-factor where I'm wrong?

You forgot to take pressure into account. This formula works assuming your nozzle is well adapted and the exit flow is at atmospheric pressure. In your case the velocity is increased but the pressure drops as stated in Bernoulli's equation.
$$P_0+ 0.5\rho V_0^2 = P_1+ 0.5\rho V_1^2$$
This means that the pressure force on your nozzle will counteract the thrust provided by the fluid acceleration.
See this explanation  your general thrust equation if the pressure are different is
$$\text{Thrust} = (Q * V)_e - (Q * V)_0 + (P_e - P_0) * A_e $$
Given $A_e$ is the exit aera of the nozzle.


What do these numbers above the terminal jetway mean for pilots? The sign above the terminal has numbers, I assume, to help the pilot park.  What do they all mean?

That's a countdown to the Target Off-Block Time (TOBT) showing 67 minutes to go. The minus is like the T minus 5 for a rocket launch.

[TOBT is the] time that an Aircraft Operator (AO) or Ground Handler (GH) estimates that an aircraft will be ready, all doors closed, boarding bridge removed, push back vehicle available and ready to start up / push back immediately upon reception of clearance from the Tower. (...)
TOBTs will be displayed on the Stand Entry Guidance System (SEGS) for every flight at 'Actual in Block Time' (AIBT) or 75 minutes before a departure. The countdown clock is in line with the latest TOBT update. Please see Fig.2 [emphasis and link added]

gatwickairport.com

The display design will vary from airport to airport.
Since in your photograph there's no jet bridge (no actual docking), the display is mounted separately and is not used for parking guidance. Thanks to @fooot for identifying the airport, here's a press release on SEA's general implementation.
The guidance (and information) system at SEA (where jet bridges are used) uses "infrared laser and patented 3D scanning technique" to identify the plane type, distance, and orientation – unlike the older left/right parallax-based guidance.


Do crosswinds affect which pilot lands the plane? I know the crew usually decides ahead of time which pilot is to be PF for each phase of the flight. If, when they arrive at their destination they discover a considerable crosswind component, does that ever change that decision? It seems that the upwind seat would have a considerable visual advantage. (or maybe that isn't true?) Also, do airlines have guidelines on things of that sort requiring that the PIC fly the landing?

Never ask a question with "ever" in it - because the answer will very rarely be no!

For example - if one pilot is training, then while they may have planned to do the landing reality might dictate that they have to hand over the controls to the instructor. I'm sure the same will apply to type ratings or differences training - nobody is going to let you have a crack at a severe crosswind landing during your first front-seat flight in an A380.

Additionally, flying schools will often have strict crosswind limits and some may not grant you full "As Pilot Operating Handbook" privileges until you have [x] number of hours AFTER your test.

In other words - you may have two qualified pilots, but only one of which is allowed to land the plane!

But I'm being deliberately pedantic - I suspect you're focussing more on commercial, multi-crew operations rather than two pilots who happen to be in one aircraft and I'm not qualified to answer that bit!

I'm not aware of any requirement to take seat position into account, however.


How do logbook endorsements work? I'm just finishing up Air Force Pilot Training (UPT).

The day after graduation we are issued commercial certificates for SEL and MEL.

The military does things pretty different from the civilian world though.  I don't have any sort of physical log book of my military training in the T6 and T38.

Can I go rent a "high performance" "complex" airplane after I get my FAA commercial?  I don't have any logbook or endorsements, but all of my training would surely meet these requirements. The T-6 was 1100HP, and the T38 is an after-burning, supersonic jet.

I was hoping to take my family out flying over the holidays in a Cessna Twin.

I was home a few weeks ago and went into a local FBO and asked about renting a twin over the holidays.  They told me I didn't have the proper training in a "complex" "high performance" aircraft (they really acted like they didn't believe I was an Air Force pilot).

It almost seems like there's something about the civilian world that I'm not in the loop on.

Well you’ll have to comply with the terms of §61.73 in order to convert your military pilot ratings over to civilian pilot certificates and ratings. You would also need to obtain a logbook endorsement to operate a complex and high-performance airplane legally under the FAA’s rules.  This really should not be challenging for you.  If you really want to rent a twin i.e. a Cessna 310, a Diamond DA 42, etc.,  I would approach your FBO and ask to do a check out in the aircraft that you wish to rent.  The FBO instructor can include both the complex, and if necessary, a high-performance logbook endorsement along with the training.  I don’t know how many hours total that you have - I assume it’s somewhere in the order of 200 or so hours, which s typical of UPT grads - but FBOs may have additional minimum hour requirements to rent said aircraft.  They may also have to consult with their insurance policies to see if such a thing as feasible given how little time you have on light twin airplanes.

Keep in mind here that while you have time in real 'high performance' airplanes, GA aircraft are going to handle differently than what you’d have expected. This is particularly true of light twins which are going to be a lot more treacherous in the event of an engine failure than a centerline thrust jet like a T-38 would be.  I’ve worked as a CFI in a couple of FBOs now and have had the opportunity to check out a number of military personnel on light GA aircraft.  Out of all the people that come through those places, the highest number of accidents on smaller GA aircraft for rent were caused by airline pilots and military pilots simply because they are not used to the feel and control characteristics of smaller, lighter aircraft.  A guy can have 1000 hours in F-22s and still struggle to land a Cessna 172 because the handling characteristics are so different.   Said check out may take several hours both to get familiarized with the handling characteristics of the airplane as well as become familiar with the avionics and operation within the NAS as a civilian pilot.


What's the greatest height at which a bird has collided with an aircraft? 70% of birds fly below 1,500ft, 25% of birds fly between 1,500ft and 15,000ft, and only 5% above 15,000ft. What is the greatest height at which a bird has hit an aircraft? What species was the bird?

On November, 29 1973 a bird strike occurred at an altitude of 11,300 m over Abidjan. The engine was shutdown during the collision, and was not restarted.

Altitude

  The altitude is that recorded by the pilot shortly after the impact,
  which damaged one of the aircraft’s engines and caused it to be shut
  down. The plane landed safely at Abijan without further incident.

Source

Species

It was determined the bird was a vulture:

  The remains of the vulture consisted of five complete and 15 partial
  feathers from the wings (secondaries, lesser, and underwing coverts),
  tail, neck, and breast. Sufficient details arc apparent in these
  feathers to allow their certain identification as G. rueppellii, using
  comparative material in the U.S. National Museum of Natural History.

Source

Rüppell's vulture is a specie weighting 7 to 9 kg and living 40 to 50 years:

Source.

Record

Wikipedia confirms this is the highest collision recorded in the history of aviation:

  An aircraft over the Ivory Coast collided with a
  Rüppell's vulture at the altitude of 11,300 m (37,100 ft), the current
  record avian height.

Source

Why such altitude for a bird?

This is well above Everest height, why does this bird flies so high, where there are not so many preys, pressure is only 25% of the pressure at ground level and temperature is about -57°C?

  The reason suggested is that thinner air allows faster flight without much
  effort and saves precious energy. Flying at such a great height,
  vultures face almost no physiological problems with regard to
  breathing; they have much more efficient breathing system than other
  living beings, including humans.

  Their flow of blood enables oxygen to be extracted from air, with far
  greater efficiency than any other living being. If the flight is in
  cloudless condition, low temperature at great heights too does not
  bother them.

Source

Birds at high altitude

  The previous record altitude for a bird-aircraft collision was of a
  Mallard (Anus platyrhynchos) at 21,000 ft (Manville, Wilson Bull.,
  75:92, 1963), based on feathers that I identified from the strike.
  That collision occurred between Battle Mountain and Elko, Nevada, on 9
  July 1962.

  Other high-altitude records of birds include:

  sightings of migrating geese at 29,000 ft, over the Himalayas (Griffin,
  Bird Migration, Natural History Press, Garden City, N.Y., 1964), and

  soaring Bearded Vultures (Gypaetus barbatus) at over 24,000 ft.

Source

Vultures are a known threat to aviation, as are other birds flying high:

Images and data taken from Science Focus article

In 2010, in Scotland, a Rüppell's vulture participating to a display was caught in a wind and was lost. Aviation operators had to be notified, in case the vulture was still in the vicinity.

  With a wingspan of 10ft, it could do a lot of damage to a large
  aircraft. But it's also half the size of some of our small training
  aircraft and it could take one of them, or even a helicopter, right
  out.

Source

Damaged compressor after a bird strike (not the involved aircraft):

Source.


What's the cabin pressure of a Bombardier CRJ-900? In terms of altitude (6000, 7000, 8000, etc), what is the cabin pressure in a CRJ-900?

At max differential it's 8000 ft.  The controller operates on an automatic program schedule that lets the cabin pre-pressurize to about 300 ft below field elevation at the start of the takeoff to minimize the initial pressure drop sensation following liftoff.  It then lets the cabin altitude rise 500-800 fpm, about 1/4 of the airplane's actual climb rate, until it gets to the max differential of just over 8 psi, which gives 8000 ft in the cabin at 41000 ft.


How long is a METAR valid for after issuance? I was wondering how long is the METAR report valid for after issuance? I know some airports issue them every 30 minutes and some every hour. So I wanted to know if a METAR is issued at 8:30AM then will it be valid till next Metar report i.e. 9:00AM or is it just valid for 10-15 minutes after that ?

A METAR is a report of conditions at a specific time, so it's only valid when it's issued. It's not a forecast, the weather could be different 5 minutes later. TAFs are forecasts that have a time range, they are valid during that time range. That doesn't mean they are guaranteed to be correct, it's just a prediction.


Why are the Antonov An-124 horizontal stabilisers directly behind the wings? With the wings being on the same plane as the horizontal stabilisers, turbulent air from the wings would interfere with the airflow over the elevators making them flutter. Surely putting the horizontal stabilisers on the vertical stabiliser would be more suitable?

Flutter is the main reason why the horizontal tail on Antonov designs is mounted low. Many other transport airplanes do indeed sport a T-tail (C-141, Il-76, C-5, C-17, A400M).
Cargo airplanes with a rear ramp suffer from low torsional stiffness of the rear fuselage because of that large cut-out for the ramp doors. If the ramp doors are locked with many locking points around their circumference, this can be remedied but requires those locks to work well and reliably. The Antonov philosophy is to play it safe and assume that Russian maintenance crews will clear the plane even if not all locks engage.
A T-tail adds a significant mass on the lever arm of the vertical tail and lowers the eigenfrequency of the rear fuselage. This brings the torsional frequency of the tail in the range of the first antimetric flutter mode of the wing, as happened on the C-141. Putting the horizontal tail low avoids this and allows for a lighter structure.
Since the wake of the wing moves down with the downwash angle, it passes below the tail of the An-124 in cruise. Not by much, but enough to keep flow over the tail clean. At higher angles of attack the wake will hit the tail, but those should not be encountered in normal operation. If that happens, the main effect is a lower dynamic pressure on the tail, not flutter. For that to happen, you need some coupling of aerodynamic and structural oscillations. For slow flight speed, the wing flaps will bring the wake again well below the horizontal tail.


What are technical and aerodynamical limitations to blown wings main propulsion? Why wouldn't some blown flap or blown wing device (suppressing propeller or fan or jet exhaust from aircraft design) produce sufficient thrust needed for takeoff and cruise flight, opposed to "only" providing stol capabilities at low speed?

In a nutshell, it's the inefficiency of expelling air out a long skinny nozzle which results in massive energy losses due to friction.  In other words, too much duct surface area relative to the amount of total air volume.


Can plane climb without increase pitch angle? As I know plane climb "with nose up", but can plane climb without change pitch angle?
Can I force plane to climb like this:
If I  fly in straight level flight at 100km/h and now increase just speed at 180km/h without any change at tail/wing.
1.Will plane climb with no change in pitch angle?
2.Or maybe will plane pitch up by itself?

Basically a plane will climb, descend or maintain altitude depending on two things: the angle of attack of the wing, and airspeed.
So, yes, it is possible to trasition from level flight to climb just by increasing speed, because as the speed increases, there is more airflow around the wing, and it will create more lift.
Also, generally planes have a natural tendency to pitch up if speed is increased and nothing else is done, further adding to the climb speed. Aeroplanes tend to "try" and maintain the speed they are trimmed to, hence the upward pitch as the plane is seeking to shed the excess airspeed by transitioning the extra energy into altitude gain.


Why are true and indicated airspeed different? So, I understand that True air speed is the motion of aircraft relative to air around it. And, indicated airspeed is speed arising due to dynamic pressure.
Considering a true airspeed of 100 knots, that means the air molecules are striking the aircraft at 100 kt/ vice versa.
Shouldn't this make true and indicated airspeed same?
Also with constant indicated airspeed, why does true airspeed increase with altitude? Shouldn't it remain same?

Air pressure reduces with altitude, so while an individual molecule is striking the the aircraft at 100kt, there are fewer of them. This means there is less pressure placed on whatever surface is being struck.
The difference in indicated speed is simply one of a physical limitation with the air speed indicator - air speed indicators rely on dynamic pressure/ram air to give a readout. Because of that reduction in pressure, the readout begins to diverge from the true, physical speed as air pressure differs from the reference pressure of the gauge.
It would be possible to create an airspeed indicator which adjusts for this, in the same way as the altitude indicator does. However, as it happens, the planes flight characteristics also changes as pressure reduces in much the same way as the air speed indicator does. Because of this, for pilots, the IAS is the important speed outside of navigational purposes.
Hence, all design speeds are written in Indicated Air Speed and can be referred to at any altitude.


Is it possible for an airplane to enter another airplane? I was making some cool fictional airplane designs and realized that most of my larger airplanes have a bay inside that stores a plane or two. But then I thought, is it even possible to make a plane exit and enter a plane mid-flight? Such a plane to enter another plane would need to have folding wings to take up the least space when stored, and also because the plane it is entering would have to be significantly larger to have a fuselage wide enough to fit a smaller plane's entire wingspan. Note that I am questioning if it is possible to do something NOT in an emergency, but as a tactic or for other reasons. That being said, the question differs from an emergency situation due to the fact that the question is implying that the operation be done over and over, and not in a risky, dangerous, last-resort fashion.
This mainly branches two questions:
Is it possible for a plane to exit a plane mid-flight, and if it is possible for a plane to enter a plane mid-flight. Clearly the plane must enter and exit through the belly of the larger plane, because something like a large hydraulic arm would be necessary to "grab" the small airplane and allow it to fold its wings up before hoisting it into the plane. This came to mind after considering that the plane must folds its wings up before entering the plane, and it also must take at least 5 seconds to fully fold the wings. So, folding the wings mid-flight independently isn't a good idea: The plane will plummet without wings to lift it. And to exit a plane, I'm assuming the arm will have to hold the plane out of the bottom and allow it to fold the wings out before dropping it. But here's what challenges that idea: When the arm is holding the plane and plane's wings are extended, will the little plane's wings effect the flight of the Larger plane? (Since the arm is grabbing it, it is the equivalent of the large plane having two tiny wings below it) and also, what are the effects of dropping a plane mid-flight? Any help on this would be very, very appreciated.
Oh, and a side-question from the above: Would a plane large enough to fit another plane be large enough to reasonably carry the weight of that smaller plane? And if so, how will the larger plane fair considering the fact that such a hydraulic arm necessary for mid-flight entry and exit of the large plane must be considerably heavy?

Clearly the plane must enter and exit through the belly of the larger plane

Why so? If you drop this condition, things become much easier, because you could attach the smaller planes externally and avoid folding the wings. And this was indeed tried and even used operationally.
The concept is generally termed as Airborne aircraft carrier. The first (?) and most obvious application of the idea was with airships, where the airplanes could indeed be stored internally.

Wiki
Russians extensively tried the idea in the 1930s with up to 5 fighters attached on or under the wing of a large bomber.

Wiki
Admittedly, this configuration was mostly indended for deployment of the fighters, which would then land normally. This way it was used several times successfully for bombing raids early in the WW2. Recovery of fighters was tried, and some configurations even assembled in the air rather than on the ground. But it was quite difficult and required considerable skills even without any folding wings.
During the tests, on some occasions, there were problems (including at least one fatal incident) you are worried about, namely negative influence of the fighters on the carrier. Mostly they were related to failures, when the attachment broke down or didn't work as expected (sometimes due to incorrect control of the fighter during the process).
However, even pretty much the same idea as yours was explored in the 1970s, with the B747 or C-5 as the carrier and some "microfighters" as the payload. Apparently, the concept was deemed "feasible" but never went to an advanced stage of development. Yet today, the idea may be of some interest again with UAV aircraft.

Wiki


When an airport has helipads, why would a helicopter take-off or land on a runway? At an airport with both runway and helipad (KASH) I have seen both being used for helicopter takeoffs and landings. Is there anything that causes the helicopter pilot to choose to use the runway instead of the helipad?

I know you asked specifically about runway versus helipad departures, but I thought I would lay out all the options available to the heli pilot, and you can see what all the choices are.

There are three different areas on an airport that a helicopter can operate from:

Non-movement area -- this is the area of the airport that is not controlled by the ground or tower controller. It often consists of aircraft parking areas or an area leased by a tenant.  It is separated from a movement area by this the marking below. Helipads may be found in non-movement areas, such as the Coast Guard helipads at SFO and JFK.
Movement area -- this is the area of the airport controlled by a ground controller, and separated from the runway area by this marking: . Helipads can be found in movement areas.
Runway area -- this is the area controlled by the tower controller, and contains the runways used for landing and departing traffic.

This picture from KHWD shows the three areas:

Regardless of which area is used, almost heli departures from towered airports are coordinated directly with the tower controller because the aircraft enters the controllers airspace.

At non-towered airports, helis operate out of the flow of fixed-wing traffic, and need to self-announce like any other aircraft.

Additionally, helicopters can make three different kinds of departures:

max performance take off -- which begins with a near-vertical segment, and then transitions to a horizontal. This is typically used from a confined area, and looks something like this:
normal takeoff -- this begins in an in-ground effect hover with a horizontal segment until translation lift is assured, then transitions into a climb:
running takeoff -- when there is insufficient power to begin with an in-ground effect hover, then the helicopter may begin its departure by sliding (skids) or rolling (wheels) along the ground, until translational lift can be obtained, then transitioning into a normal takeoff:

The choice of departure area and departure type are for the most part independent, but they are obviously linked based on performance and obstacles.

The departure area is an operational decision. When the helicopter is operating from a remote part of an airport, the pilot will often make a departure from a non-movement area (helipad or ramp) so she doesn't have to taxi to the runway.  If the helicopter is a passenger flight, such as air-taxi, it will most likely operate from the runway or a helipad in the movement area.

The departure type is a performance decision, based on obstacles, weather, weight, and available power. Hot & high departures might require a running take-off. Lightly loaded twin-engine copters in normal weather can safely make high-performance departures over obstacles in the desired direction of flight.


What is this jet seen in the Falcon Crest TV series? This is another jetliner from "Falcon Crest" I'm trying to identify.  It was visible briefly in episode # 194 <8.11> "True Confessions" (1989).  Thanks for your help!

I believe that it is an Israeli Aircraft Industries Westwind. This is based on the mid-set wing and the 5 windows on each side.

Image source: https://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/IAI_Westwind_%282323424886%29.jpg/300px-IAI_Westwind_%282323424886%29.jpg


What are the physical/aerodynamic implications of designing a prop guard for multirotors? A number of drones these days like the one shown in the picture below have  fully protected multi-rotor propeller guard system . These are lightweight, aerodynamic housing that keeps these spinning knife-blades away from people's fingers, trees etc.

So,what are the  physical/aerodynamic implications of designing a prop guard for a multirotor drone whose specs are as follows:

All Up Weight with battery: 1050g
Frame weight empty (no electronics, motors, or battery): 400g
Flight time with 3s 2200mah lipo: 8 minutes
Propeller size : 10"
Skeletal Plastic Structure

Source: Safe Flight Copters

Aerodynamically, one can say that those prop guards create some kind of Fenestron (Like some tail rotors in helicopters), which will reduce the tip losses of the propeller.

On the other hand, they will increase drag in forward flight, reducing the UAV top horizontal speed. If you take a look at the Aibotix X6 you see a one piece prop guard designed aerodynamically to reduce drag in forward flight.
In the particular case of your image, the black web also decreases the area of air flow into the propeller, certainly reducing its efficiency.

Another prop guards disadvantage is the weight they add. Even though they might be made of lightweight material, they have to have some strength to resist any impact.

To sum up, with a prop guards like those, you should loose top speed and around 2 minutes of flight time.

One last tip: if you want to fly your UAV close to trees, forests or power lines, be careful with the prop guards because you might end with your UAV hanging on a tree branch 10m high... (happened to me :/)


Is it possible to hand start modern planes? I know that older planes must be hand started but are newer GA planes even able to be hand started by spinning the prop?  If so, how do you do it safely without cutting your hands off or being pulled in by the propeller?

You sure can!

In reality the engines in modern prop planes are not all that different (in some cases even identical) to the engines of the hand crank days. The reason many older planes were hand crank was simply to save the weight toll of a starter motor and battery to drive the system. Some older aircraft have no active electronics (the piper cub comes to mind). Remember the engines magnetos drive the spark for the ignition system unlike in a car where the spark is driven by the electronic system. As long as proper precaution is taken its more than possible. The FAA even explicitly discusses it in their airplane flying handbook (p 2-13)

  A spinning propeller can be lethal should it strike someone.
  Historically, when aircraft lacked electrical systems, it was
  necessary to “hand prop” an aircraft for starting. Hand propping an
  aircraft is a hazardous procedure when done perfectly. The
  consequences of not mitigating the hazards associated with hand
  propping can lead to serious injury, fatalities, and runaway
  airplanes. All alternatives must be considered prior to hand propping
  an aircraft and, when a decision is made to do so, the procedure must
  be carried out only by competent persons who have been trained to
  accomplish the procedure, understand how to mitigate the hazards, and
  take all the necessary precautions.

They also provide a pretty clear checklist on how to do it.

  The procedure and commands for hand propping are:

  • Person out front
  says, “GAS ON, SWITCH OFF, THROTTLE CLOSED, BRAKES SET.” 2-14

  • Pilot seat occupant, after making sure the fuel is ON, mixture is RICH,
  magneto switch is OFF, throttle is CLOSED, and brakes are SET, says,
  “GAS ON, SWITCH OFF, THROTTLE CLOSED, BRAKES SET.”

  • Person out front, after pulling the propeller through to prime the engine says, “BRAKES
  AND CONTACT.”

  • Pilot seat occupant checks the brakes SET and turns
  the magnetos switch ON, then says, “BRAKES AND CONTACT.”

As far as i know, you can not hand start a turbo prop (which some GA planes have) due to the higher RPM needed for start.


Do UAVs use ground-based navaids? When I Googled it seems it is not common to use Vortac like systems from UAVs as a backup to GNSS outages, like in manned aircraft. And also I haven't seen any equipment designed for just UAV platforms, it's all designed for in-cockpit use.

Why do UAVs not use ground-based navaids?

For UAS, the aircraft may be below the service volume of a VORTAC most of the time.  Furthermore in the US sUAS are normally line of sight to the pilot so in theory if GNSS is unavailable, the pilot will control visually.  Finally the variability and uncertainty of VORTAC is high enough so as to make it impractical for UAS stability, drift and position control


What is the best way to retrieve (and transmit) location (GPS) of plane in real time? What are some of the best ways to retrieve and transmit the location of a plane I am in, real time.

To speak in realistic terms, I'm currently training for my private pilot's license and as such am spending a lot of time in various planes I do not own / have decision powers over. How could I share my current location with someone in a remote location while in the air without physically modifying the aircraft.

There are a couple of ideas that have come to mind, but my understand of the solutions or challenges are not complete:

There are websites like flightradar24.com, but the aircraft I'm in often don't show up. That being said, a flight I took yesterday DID show up, but was not terribly accurate. Perhaps that is because I filed a flight plan and / or used flight following (which would put me on the radar tied to my tail number).
I could use a simple app like "Find my Friends" on the iPhone. I realize this is crude, but it could work. That being said, I don't know how well cell phones transmit above the ground.
Some other portable device. That device would need to transmit real time in some way and there would need to be some way to look up that transmission.

Any information on this would be appreciated!

UPDATE:
I'm talking about general aviation here. Speeds <= 120 kts altitude typically <=  5,500

There are a few consumer-facing easy-to-obtain devices that you could use for this, although they don't quite transmit in real-time (they'll transmit updates down to every 2 minutes).  Spot and inReach are aimed at more casual users, and Spidertracks offers real-time tracking that might be considered targeting more of the commercial or "prosumer" market, but they still transmit updates every 1-2 minutes.

They all work in a similar fashion: rather than some kind of ground-based radar, they utilize a combination of GPS to calculate your location and use the Iridium Satellite communications network to transmit it (so it doesn't rely on cellular signals and has global coverage), they transmit on an interval you decide to a website that your interested party could monitor.  This is the key difference from other answers that use an app on a device: even if the app is linked to a real-time tracking service like Map my Tracks, your phone or tablet will still be relying on the cellular network (which you're technically not supposed to be using in flight), and even if it does work, it could be intermittent. These devices link into the Iridium Satellite network for global coverage.

The three devices are: Spot Satellite Communicator and the DeLorme (now owned by Garmin) inReach, and Spidertracks.

This isn't a free service, there is a monthly fee for using the devices.

Spot is around USD$150

inReach is around USD$350

Spidertracks start at USD$1000

In July 2016 ($USD)

inReach: Allows tracking updates every 10+ minutes ($15/month) or the 99/month package allows for updates every 2+ minutes.

Spot: 50/year allows 5, 10, 15... minute tracking update intervals or $150/year: 2.5+ minute tracking updates.

Spidertracks has various plans, basically you pay by reporting point the range is $0.05 - $0.13 per reporting point.

DeLorme inReach:

Spot Satellite Personal Tracker:

Spidertracks

Example of the web interface from Spidertracks for real-time tracking


How much power is drawn by a turbofan to power its own compressor? In a modern commercial airliner how much percentage of its engine power is used to power its own compressor, the ducted fan and other ancillaries like the airconditioning etc? Maybe it can't be calculated with accuracy but I'm looking for at least an approximate figure.

To answer this question, it is best to start with the compression work which has to be performed on the air flowing through the engine. If you just want to know how much power is needed to run the fan on a mid-sized passenger jet, you can look at industrial installations of the Rolls-Royce RB-211, two of which power the Boeing 757 and four the Boeing 747-200. The electrical output comes directly from the low pressure turbine which would drive the fan in an airliner engine, and is up to 32 MW for the RB-211 (after generation losses).

Now to the core compressor: If we assume that no heat is exchanged between the gas and the surroundings we can use the formulas for the adiabatic process as presented in Wikipedia. The example given is actually a nice fit for the RB-211-535 or an EJ-200 engine:

Initial state (Index 0): 27°C/300 K and 1 bar/100 kPa

Final state (Index 1): 477°C/751 K and 25 bar/2500 kPa, 10% of the initial volume.

When we use this Wikipedia page, we get:
$$W = \frac{\kappa\cdot R\cdot(T_1 - T_0)}{\kappa - 1} = \frac{\kappa\cdot R\cdot T_0}{\kappa - 1}\cdot\left(\left(\frac{P_1}{P_0}\right)^{\frac{\kappa - 1}{\kappa}} - 1\right)$$

where $R$ = 287 $\frac{J}{kgK}$ is the gas constant and $\kappa$ = 1.4 for diatomic gasses like nitrogen and oxygen.. $V_0$ of 1 kg of air is 0.84 m³ and $V_1$ is 0.084 m³. The result is $W$ = 454 kJ per kg of air, and that has now to be multiplied with the mass flow. For the RB-211 I find mass flow data only for industrial applications where the engine runs at a reduced pressure ratio, but I will use the 203 - 212 kg/s regardless because it fits with the initial pressure and temperature data of my example. The result is in the order of 95 MW in a 200 kN thrust class engine.

Considering that the above equations are for the ideal, friction-less case, the true power need is probably 10% - 20% higher. However, at altitude the air density is only a quarter of that at sea level, so the compressor power needs are also only a quarter.

To put it into proportion, we need flight speed as well: At 240 m/s the 50 kN thrust at altitude translate into 12 MW of propulsive power, so the compressor power under the same conditions is twice as high.


When was the first rudder on an aircraft used? I have seen pictures of World War I-era airplanes that have rudders much smaller than today. When did the first rudder come out?

Planes as early as the wright glider (1902) had a rudder, it appears from pictures that the 1900 and 1901 variants did not have rudders but its hard to tell from the photos.

Depending on your definition if you are talking about powered flight the Wright Flyer (1903) had 2 rudders much like its earlier glider predecessor.

In the lighter than air category, the Giffard Dirigible (1852) had a sail like rudder in the aft of the ship. So that may take the cake if you have consider it a true rudder.

Side Note: Patented in 1930 the V-Tail design could be argued as the first design that did not (as far as I know) employ a rudder. The earlier Beechcraft Bonanza's are the most common plane of that design in commercial production. There is quite a bit of debate as to the safety of ruddervators and the general theme seems to be that they are not perfect and do require some care to fly properly.


Why do I get that funny stomach drop feeling right after takeoff? Right after take off 1-2 minutes into flight I get this stomach drop "roller coaster" feeling for split second.  It freaks people out thinking they are about to crash!  Why is that??

It happens when the airplane levels off after takeoff, usually either at the first assigned altitude or at a safe altitude where it will be accelerated in order to retract the flaps.   The feeling is a result of negative vertical acceleration.  It can also happen at other times during the flight, such as during turbulence or when starting a descent.

Basically you and the airplane are both in a steady climb and when the aircraft levels off you continue to move up faster so it (via the seatbelt) keeps you at its same level and decelerates your own personal vertical climb.

It is just like the feeling you get in a roller coaster.

My wife calls it a wee-hill!  :-)

EDIT:

Another more familiar example happens anytime that you are traveling in a car:

If you are in a car moving at a constant speed (let's say 55 MPH) you are moving at the same speed along with it.

When the brakes of the car are engaged, they slow the car down but your inertia tends to keep you moving in the direction that the car was going.  This will be more noticeable as the brakes are applied harder and harder because the deceleration of the car is more extreme.

You will notice this as pressure against the seat belt as the car holds you in place.  You are still moving forward, but you are getting slower (decelerating).  In an airplane the exact same thing is happening only it is in a vertical direction instead of a horizontal direction like in the car.

What you are feeling is your stomach floating up a little inside your body, because while the seat belt is holding you down, it doesn't hold your stomach in place!


How do GLS avionics plot an entire accurate approach path? I'm studying wireless navigation systems, especially GBAS. I have gone through some ICAO documents regarding GBAS. From what I have read, FAS data is included in Message Type 4. Closer examination of FAS data block tells that there is no block ID or sequence number which suggests that FAS data is not sent in chunks.

My question is, how does the on board equipment plot an entire accurate approach path? Since FAS data block has just the coordinates for LTP and FPAP.

I'm not a pilot so my understanding of operational details regarding GLS is pretty basic.

The best reference is the ICAO GBAS Guide.  Unfortunately, it doesn't have diagrams to help understand it.

The Final Approach Segment (FAS) is a geodesic path to the runway. It is horizontally aligned with the runway center line and has a glide path angle that descends to the Threshold Crossing Height (TCH) directly above the Landing Threshold Point (LTP). This can be seen in the following figure:

Source: SlideShare

All the necessary data is contained in the type 4 message as the ICAO table below shows:

Source: ICAO

There is one Type 4 message for each approach supported by the GBAS ground station.

The LTP/FTP latitude, longitude, and height are coded in the data block. The FPAP is coded as a delta Lat/Lon from the LTP/FTP. Horizontally, the FAS will pass through both of these points and thus be aligned with the runway center line.

The vertical component is defined by the Threshold Crossing Point (TCP which is the LTP vertically raised by the TCH) and the Glide Path Angle (GPA).


How to define the aileron's deflection angle (in the Laplace domain)? Very simple question here. I know what Laplace transforms are, but except for solving ODE's I haven't really used them in a real project or thought about it in a very pragmatic way.

I am currently reading "Small Unmanned Aircraft : Theory and Practice" from    Randal W. Beard, Timothy W. McLain and am a bit lost on how exactly I should incorporate/use a specific equation.

My question is about this equation that relates the aileron deflection to the fixed wing UAV's roll angle:

where:

It seems like the aileron's deflection angle $\delta$ is a function of s, ie $\delta(s)$.

So my first question is: suppose you want to imply the aileron rotated 45degrees how does that translate to $\delta(s)$?

Secondly, I imagine I should let s vary from 0 to infinity, that will give me a graphical representation in the s domain, but that I think won't tell my how many degrees my roll angle is relative to some axis. Or am I missing something?

EDIT:

Another link to the book, with mirrors (libgen.io, libgen.pw, bookfi.net, bookzz.org) to its content depending on your location: http://libgen.io/book/index.php?md5=7314182B194BAB33173B521614B42663

I am trying to achieve latteral tracking and/or terminal control on a fixed wing UAV for autodidactical purposes.

It looks like a transfer function for a feedback loop, which is a function of time and transformed into the frequency domain. Input is the aileron deflection $\delta(s)$, output is the roll angle $\phi(s)$. When deflecting the ailerons, the aircraft is accelerated around the X-axis. The roll movement creates a damping force proportional to span $b$, which quickly dampens out the roll acceleration into a steady roll rate.

So achieving a roll angle depends on the moment of inertia around the X-axis, and wing area geometrical data, plus the time that the aileron is deflected at a certain angle. In order to get to a specific bank angle, the aileron needs to be deflected, then returned to zero before the bank angle is achieved - damping and inertia will then continue to roll the aircraft until the target bank angle is achieved.

The transfer functions defined in the frequency domain are used for determining gain and phase shift, more info for instance here, section 6.3 onwards. Using a signal in the frequency domain gets to be a pain once the deflection is a real world time history and not a mathematical function like a sine wave or a pure step input.

Image source

Once the gains are determined with the Bode plots, the block diagram of the transfer function is pretty useful for determining bank angle as a function of the time history of aileron deflection: just read the actual bank angle, subtract from the desired bank angle, and set the aileron deflection angle in real time according to the difference signal.

EDIT

Have managed to have a look into the book. I'm familiar with the equations, describing stability and control of aircraft. Your question on how to define an input signal in the frequency domain is a pertinent one: it would have to be defined mathematically in the frequency domain as well. I have only seen use of the frequency domain equations in off-line analysis, not in real-time use since the inputs are never purely mathematically defined. Equations such as 5.53 for the time domain. Then any input signal can be added in real time, multiplied with the gains found from the Laplace transform, integrated and output.

  So my first question is: suppose you want to imply the aileron rotated 45degrees how does that translate to δ(s)?

It depends how fast you bring the ailerons to 45º, for how long you keep them there, and what happens next. If it is a step response, the function is $\frac{0.785}{S}$. The aircraft will respond with a steady roll rate (in aeroplane axes) and will never establish a constant bank angle.


Is there an alternative (more robust) operating law/setting for jet-engines? After one engine failed? Sorry for the complicated Question.

I was wondering (after reading this report) if a two-engine air plane has an alternative operating scheme/setting for the remaining engine. Maybe a setting which is not that fuel efficient but more stable with respect to compressor surge and stall.

In the cited report one engine suffered compressor stall (maybe by bird-strike) and was subsequently shut down. The other engine was reported to have left a trail.

Aircrews regularly practice emergency procedures for engine out scenarios in their training and simulations.

Aircraft manufacturers and airlines provide procedural outlines for various possible emergency conditions specific to the type of aircraft.

During an in flight emergency, fuel efficiency is not a priority. The aircrew is to ensure safe flight of the aircraft and the priority becomes landing quickly and safely. This may require use of the engine in any fashion to keep the aircraft in flight.

In the report you reference, there is no real way to know what (if anything) caused what appeared to be a trail of smoke seen by another person in another aircraft waiting to take off.


Under EASA regs who is responsible for part m continued airworthiness? Lessor or Lessee? If an aircraft is leased out by a lessor to an operator does the lessee (operator) take full responsibility of continued airworthiness or does the lessor have some liability?

Perhaps it's similar under FAA law?

It really comes down to the lease contract.  I don't think any of the regulatory authorities much care who pays to maintain it or what's in the lease contract, as long as the airplane is airworthy when it leaves the ground, which is basically up to the operator.  What we are really talking about here is who pays.

Pretty much anywhere, the lessor is expected to deliver the unit in an airworthy condition, then the lessee is expected to maintain it and return it to the lessor in an airworthy condition at the end of the lease. Like a car.  But it depends on the details in the lease.

The lessor is frequently a non-operator (Like GE Capital) who has no means to maintain the airplane in the first place so in any case it's the airline that will actually do the work, or contract the work, for something like an AD.

Who is on the hook to pay for Service Bulletins and AD compliance will be up to the lease contract (on an aircraft that is out of warranty).  If someone leases an out-of-warranty airliner from GE Capital, and the contract says that GEC will pay for ADs, then the airline will do the work but charge back the expenses to GEC.

Plus, GEC may have a clause in its purchase agreement with the OEM to cover AD costs beyond the warranty period and extend that protection to the lessee.  There are large variations in terms and conditions between OEMs, leasing companies, and airlines on a given type, as it's all part of a negotiated package.


What causes hunting movement in helicopter rotors? The blade of an helicopter rotor can have three hinges: pitch hinge, flapping hinge and lead-lag hinge.

Lead-lag (dragging): movement of a blade forward or aft in the plane rotation. Lead lag is facilitated by a lead-lag hinge in the rotor system or through rubber like bearings that allow individual rotor blades to move back and forth in their plane of rotation.
This helps balance the blade system and reduces vibration. The drag brace or drag damper resists the movement of the blade around its lead-lag hinge on a semi-rigid rotor system.

In the same plane, we have also the hunting, defined as the tendency of a blade to oscillate ahead of or behind a position which would be determined by centrifugal force alone.

Why should the centrifugal force alone determine a movement aft and behind the plane of rotation?

Lead lag is caused by the blades speeding up and slowing down as they flap up and down.

The blade on the advancing side experiences an airflow equal to it's speed plus the forward speed of the helicopter.  The blade on the retreating side experiences airflow equal to the speed of the blade minus the forward speed of the helicopter.  This causes dissymmetry of lift.

To counter this, the blades can flap up and down around the flapping hinges.  The blade on the advancing side flaps up, reducing the angle of attack and therefore the lift generated.  The blade on the retreating side flaps down, increasing the angle of attack and therefore increasing lift.

See this video at around 1:30 to see flapping in action.  This is a gyrocopter, but you can really see the blades flapping on this one at 0:39 and 1:17.

Due to conservation of momentum, the blade flapping up speeds up as it's centre of gravity moves inwards toward the rotor hub.  Since the rotor is turning at a constant speed, the blade must move forward around the lead/lag hinge.  In a similar way, the blade flapping down slows down so lags.

The blades will hunt forward and backwards from the neutral position in a sine wave as the rotor rotates.  Lead/lag dampers reduce the force of this hunting.

A variation of flapping hinges (independent hinges for each blade) is a teetering hinge on 2 blade helicopters where the hinge is connected to each blade.  If one blade rises, the other must fall and vice-versa.  The entire rotor disc "teeters" on top of the drive shaft.  This is known as a semi-rigid head and as far as I know, is used on all 2 blade helicopters.

In semi-rigid and rigid heads, the overall effect of the blades speeding up and slowing down cancels out in the complete cycle of rotation and other mechanisms are used to reduce the hunting loads.  Imagine a 4 blade rigid rotor.  2 blades are trying to speed up the rotor and 2 are trying to slow it down in equal amounts.

One serious side effect of lead/lag on fully articulated heads is ground resonance.  Since the blades can move forwards and backwards, it is possible for the blades to get closer together on one side than on the other, especially when the helicopter lands with a roll angle, so one gear hits the ground first.  This shifts the centre of balance away from the centre of rotation which can induce a wobble of the rotor head, which translates into a vertical "bounce" vibration at the landing gear. If conditions are right (or wrong, depending on your view point), the resonance can be amplified by the natural resonance frequency of the helicopters landing gear and can lead, if allowed to continue, to the destruction of the aircraft.

If you think that helicopter blades are quite rigid, think again.


Does simulator time count as time in type? Can full motion simulator training time (FSI) be counted towards the required 100 hours that a part 135 captain is a High Minimum Captain?

Unfortunately, no.

135.225 - IFR: Takeoff, approach and landing minimums (e) requires:

  The MDA or DA/DH and visibility landing minimums prescribed in part 97
  of this chapter or in the operator's operations specifications are
  increased by 100 feet and 1⁄2 mile respectively, but not to exceed the
  ceiling and visibility minimums for that airport when used as an
  alternate airport, for each pilot in command of a turbine-powered
  airplane who has not served at least 100 hours as pilot in command in
  that type of airplane.

So this means that our question becomes:  Can a pilot log PIC time when "flying" a simulator?

The answer to this question comes from 61.51 - Pilot logbooks, where you will notice that none of the bold parts (marked by me) have been met in the situation that you describe.  Generally, PIC time requires you to be PIC of an aircraft, and does not provide for PIC time when in a simulator unless you are providing instruction:

  (e) Logging pilot-in-command flight time.

  (1) A sport, recreational, private, commercial, or airline transport
  pilot may log pilot in command flight time for flights-

  (i) When the pilot is the sole manipulator of the controls of an
  aircraft for which the pilot is rated, or has sport pilot privileges
  for that category and class of aircraft, if the aircraft class rating
  is appropriate;

  (ii) When the pilot is the sole occupant in the aircraft;

  (iii) When the pilot, except for a holder of a sport or recreational
  pilot certificate, acts as pilot in command of an aircraft for
  which more than one pilot is required under the type certification of
  the aircraft or the regulations under which the flight is conducted;
  or

  (iv) When the pilot performs the duties of pilot in command while
  under the supervision of a qualified pilot in command provided—

  ...

  (2) If rated to act as pilot in command of the aircraft, an airline
  transport pilot may log all flight time while acting as pilot in
  command of an operation requiring an airline transport pilot
  certificate.

  (3) A certificated flight instructor may log pilot in command
  flight time for all flight time while serving as the authorized
  instructor in an operation if the instructor is rated to act as
  pilot in command of that aircraft.

  (4) A student pilot may log pilot-in-command time only when the
  student pilot—

  (i) Is the sole occupant of the aircraft or is performing the
  duties of pilot of command of an airship requiring more than one pilot
  flight crewmember;

  (ii) Has a solo flight endorsement as required under §61.87 of this
  part; and

  (iii) Is undergoing training for a pilot certificate or rating.


Which category is A321-271NX in? So I was wondering what is the Aircraft categories all about because from my previous questions answer I got to know about something called Cat D type aircraft so it made me curious to know what are the different types of aircraft categories and which one is the A321-271NX because it happens to be special for me !

The code is for the exact variant for this Airbus:

A321: This is an Airbus A321, the longest variant of the A320 family.

27*: It comes with PW1100 engines (which makes it a neo).

271: The exact engine variant, which can be found in the TCDS (Type Certificate Data Sheet):

PW1133G-JM Geared Turbo Fan jet engines (MOD 161002)

N: Added for all neo variants.

X: This means the aircraft has Cabin Flex, which allows the operator more freedom in choosing emergency exits:

these doors’ configuration flexibility are there to enable all customers’ operational needs without compromising on cabin comfort

(runwaygirlnetwork.com)

The "Cat D" you mentioned is the approach speed categorisation:

Category
Approach Speed

A
< 91 kt

B
91-120 kt

C
121-140 kt

D
141-165 kt

E
166-210 kt

The Airbus A321 can be in approach category C or D, depending on the maximum landing weight:

A321 has Approach Category C to 75.5 tonnes MLW and D beyond that to 77.8 tonnes.

(SKYbrary - Airbus A321)
You can find the maximum landing weights for the A321neo in the Airbus Aircraft Characteristics Document:

All maximum landing weights for the A321neo are above 75.5t, which would make them all Cat D.


What unique challenges/limitations will I face if I start a career as a pilot at 45 years old? I'm contemplating a mid-life career change. I made some money in another industry, and now have the luxury of choosing a job that pays less, but provides enjoyment and satisfaction. I suspect being a professional pilot could be the ticket. I'm currently an active glider pilot with 300+ hours, and I am just loving it! I learned to fly gliders very quickly and I am confident that I could learn to fly powered aircraft quickly as well. Fortunately, I can afford the training and the cost of building up hours, potentially in my own plane.

I know it takes a long time to work up to flying an airliner, but I'm not sure that's even what I want to do. Flying smaller planes appeals to me more.

Am I crazy to try to start a piloting career at my age (45)? Is the system going to be biased against an older trainee like myself? Should I go to an aviation college? Will I ever make a decent salary given how many working years I have left? Also, see the question in the title. Thanks.

Time

All other things aside all commercial part 121 pilots have a finite end date, starting at 45 means you are going to be ~20 years behind the young guys. Since the FAA mandates retirement from part 121 operations at 65 you have 20 years left but let's look at that a bit more practically. Assuming you pay for all your own training and don't need to go the CFI route to build hours you could conceivably finish your 1500 ATP hours in a year's time if you flew full time and the weather gods were nice to you. However that's not really realistic for all kinds of reasons, weather, mechanical, practical etc. So let's say you get there in a modest 2 years. Now you're 47...

At 47 you are applying to the airlines, still need to actually pass your ATP exams, and then they need to type you into one of their aircrafts, that's simulator time and ground school time for the airline which is by no means free and takes time - this means you are getting older. They are investing in you and in their eyes they can now only get 17 years or less out of that investment unlike the young guys they may have for longer. A regional may be interested but expect long grueling days and pay on the lower side of things.

You are also starting at the bottom of the seniority tree. If you are accustomed to a nice self sufficient lifestyle now you, should not expect that working at a regional for the first few years.

There are lots of other flying jobs that are not bound by the 65 year old limit, they may be a bit more transient in nature but you can still get into a high performance airplane and be having fun. You can fly for a part 135 charter operation, be a flight instructor, tow banners, tow gliders, crop dust, fly sight seeing flights, etc. One job that I have spoken to a few professional pilots about that seems like a sweet deal is being on staff flying a corporate jet for a company, the hours tend to be decent, you end up flying some fast metal and going cool places.


Is the Inspire 1 a good drone starter aircraft? First of all, I'm not totally positive that this will be well received here; I did read the related meta, but am unsure. I have also asked the question in support of the new Drone SE.

I'm new to drones, and I've been researching. Would it be a bad idea to start out as a beginner with the Inspire 1 (sort of the cutting edge, top of the line, nicest looking drone out there)?

I read somewhere that with Drones, unlike normal RC aircraft, (and large aircraft perhaps) the higher the price, the easier the flying. I'm worried about whether or not getting a very high end drone as my first one might prove a foolish investment?

I'm not sure this question will remain open long but here's my $0.02:

You will definitely want to learn to fly a cheap quadcopter before going expensive. Quadcopters are not that easy to fly (there is a lot going on at the same time: 6 degrees of freedom being controlled in a changing frame of reference depending on orientation to a stationary pilot).

I crashed my cheap one a lot learning to fly it despite it being pretty stable, but it is robust and takes a good beating. A cheap one is a very low risk and pain compared to the one you're looking at: You're not going have to break a lot on the expensive one to recoup the investment of becoming acquainted to quadcopters before you started.

Quadcopters may become a little 'smarter' as you go more expensive and be more stable, but it still requires good piloting.


What is this jetliner seen in the Falcon Crest TV series? I'm trying to identify this jetliner from the "Falcon Crest" TV series filmed in 1984  It's from episode # 068 <3.28> "Ashes to Ashes".  This is the only scene featuring the plane. There are other scenes with planes (stock footage) in this episode, but they feature different jetliners, which have been identified already.  Unfortunately, there's no shot of the cockpit and tail available.  Does anyone recognize this make and model, please?

It is a Grumman Gulfstream II business jet, not an airliner.
The oval windows are very unique to both the Grumman Gulfstream I business turboprop, and Grumman Gulfstream II business jet. The small engines are Rolls Royce "Spey" engines meaning it is either a Grumman Gulfstream II or Gulfstream III. (later Gulfstream versions had the larger "Tay" engines) The lack of wing tip "winglets" means it is has to be a Grumman Gulfstream II.
Grumman Gulfstream II


Why don't drones use ducted fans? If efficiency of converting battery power to lift or thrust is paramount, why don't drones use shrouded or ducted fans, instead of unshrouded propellers?

This is the only image I could find to clarify what I mean by "ducted fan":

Image source (public domain)

My thoughts:

An extremely light weight duct could be made, so weight is probably not a factor
Increased suceptibility to winds could be a big negative
Maybe it doesn't make much difference at the low thrust levels of drones

The reason not many drones use ducted fans is efficiency.
Ducted fans are great for fast forward flight but not for static lift.

Explanation: Yes, the 'duct' reduces losses at the blade tips, However, adds significant losses at the intake lip and exit where the adjacent air is pulled into the flow. For ducted fans installed in aircraft, These losses are reduced at high forward velocities and increased at low forward velocity. For drones, there is situation with perpendicular intake flow, when drone is travelling sideways and fan pointing up, there is even greater losses at front intake lip.

The most efficient blade design for static lift is to have the blade as long as possible (like a helicopter) and travelling as slow as possible. Least efficient to have short blades travelling at high velocity.

It is easier to imagine what is going on if you increase the viscosity and imagine the fluid is water instead of air. Very large blades would move water only a small about, but over a large area. however, very tiny blades would be require to move vast amounts of water through a small area to produce the same thrust. moving that much water increases drag as the blades have to suck in water at the intake and the exiting water would be slowed very quickly by the surrounding water at the exit.


What is the weight difference between 100 hp and 150 hp Continental engine? What would be the approximate difference in weight for a Continental 100 hp engine compared to a 150 hp?

Which variants are you specifically talking about?

The Continental O-200-A (100hp) weighs 170.18 lb (77.19 kg) dry, without accessories.

I can't find a 150hp Continental, so here is the closest variant I could find:

Continental O-300 (145hp) weighs 268 lbs (121.5 kg) dry, without starter or generator
The O-300 is also listed as a C-145 and as a C-175
E165-2 165 hp dry weight 351 lb (159 kg) - Variant of the O-470
E165-3 165 hp  dry weight 352 lb (160 kg) - Varian of the O-470

I hope that's what you were looking for.


Are taller landing gear bad for aircraft, particulary large airliners? Buiding larger engines for larger aircraft as opposed to smaller but many engines has proved to result in more fuel efficiency.
Having established one of the main drawbacks or impediments to building larger engines are ground clearance for engines in light of aircraft/airliners in their current under wing configuration. This configuration in light of current technological advancements seems to offer the greatest advantage in terms of control of the aircraft, stability and weight closest to the center of gravity when flying among other things.

If space to store the retracted gear were not a problem due to some new design, are taller gear for airliners necessarily undesirable for landing and take off? Do they present some technical problem if for example they were strengthened, the extra length would present some problematic leverage problems as they get closer to the pivot and "load"?

Tall landing gear has been used in the past:

The Tu-114 needed really tall gear to clear the really big props. The drawbacks are extra weight and volume, as described in the other answers.

The Tu-114 was so tall, on its first flight to the US (the prototype was used to ferry Nikita Kruschev to the UN for some shoe banging) the available boarding stairs weren't tall enough. That arrival raised some eyebrows in the West because they'd done a nonstop flight from Moscow (the Tu-114 was the first aircraft that made that possible).


Why aren't modern helicopters quieter? Living closer to a Sikorsky factory, I can attest that modern civilian (and military) helicopters are quite noisy. In any case, they are considerably louder than light aircraft, turboprops, and even some jetliners.

This has resulted in helicopters being banned from approach and landing in some jurisdictions.

It seems though, that the techniques for sound mitigation of helicopters have been known since at least the 1970s (The Quiet One) let alone the stealth helicopters used in the Bin Laden raid.

That is,  part of the solution appears to be to use more rotor blades while decreasing the speed of the rotors. There are also modifications to the tips of the rotor blades that while they may be classified, could be deduced and reverse engineered.

Why are helicopters so loud and why aren't contemporary helicopters quieter given what we know and how far we've come in materials sciences and aviation design?

Or is a question of economics (quieter == less economic) or politics (national security prevents the use of sound-mitigating technology) or something else?

It's an R&D and therefore ultimately a cost-benefits decision. Quieting techniques for helicopters aren't as simple as "hush kits" for fixed-wings, because the engines and rotors are a much more integral part of the entire airframe. So, to incorporate these features into a civilian helicopter is a much more involved process than swapping blades on a turboprop or putting hush rings on the exhausts of older airliner engines. Changing the physical properties of the rotors (lift, induced drag, moment of inertia) requires compensating changes in the engine; shorter blades reduces lift requiring higher RPM, more blades increases MOI requiring more torque, etc. Those engine changes will in turn require changes to tail rotor characteristics, and may also require frame and body tweaks, etc etc.

Most helicopters in civilian use today, like the Bell 200-series, Sikorsky S-70 family, Dauphin etc are Vietnam-era designs, almost unchanged save for a few minor tweaks along the way like incremental engine improvements or new avionics systems. They're still being built and flown because they work; take the rigorous proving tests required of any aviation system and the maintenance and inspection requirements of fixed wing aircraft, and add an additional level of caution for the inherent instability and lack of fail-safes in the design of a rotary-wing aircraft, and you'll have some idea of what it takes to get a new helicopter vetted for GA use. If the helicopter's engine cuts out or throws a prop blade, you can't just glide down to the ground the same way as a fixed wing. So, any changes you make to a basic, proven design would be subject to extreme skepticism and testing by both aviation regulators and owners, to say nothing of starting from scratch. This decreases initial sales of a new model in the civilian market, increasing the payback period of your R&D to develop this new design.

Second, in part due to this hesitance by GA to adopt new chopper designs, the funding availability to research and develop any new civilian helicopter design is dwarfed by military interests. As mentioned, practically every design you see in the skies today has a military pedigree and was designed primarily for that purpose, then civilianized for GA use (a notable exception being the Eurocopter Dauphin 2 which was established in the private and law enforcement sectors before militaries took a look). As a result, a lot of the newest stealth technologies available for helicopters, including noise reduction, are heavily classified. For instance, the modifications to the UH-60s used in the Bin Laden raid; civilians really only know that stealth Blackhawks exist, as what they look like and their performance/noise characteristics are all still top secret. That hasn't stopped the human imagination; artist impressions including the concept art for Zero Dark Thirty abound.

In addition, the civilian quiet-copter technologies that aren't classified, like Eurocopter's "Blue Edge" blade design, are mostly protected by international patent. Bell or Sikorsky can't just reverse-engineer the Blue Edge blade and stick it on their choppers. An independently-developed design must be different enough to be patentable, which probably means it will be more complex, and complexity is a bad word in aviation because it means increased probability of system failure or operator error. The other avenues would be to either license Blue Edge from Eurocopter (increasing the cost of a Bell or Sikorsky Blue Edge-equipped model) or wait 15-20 years until the patent expires (further delaying widespread adoption of the technology beyond one brand).