Instructor can't talk when H10-13.4 is plugged in I'm a student pilot and I just bought my first own headset because the standard one in the plane does not really fit me.

I got a david clark h10-13.4.
My instructor uses either his private Bose A20 or the standard (active) Aerostar that is in the plane.

Today I tried my DC-headset for the fist time and there was a problem: I could talk just fine and the mic worked great but I could not hear my instructor anymore. He had to yell into the microphone to activate the intercom and even when he was loud enough, the sound quality was aweful. This was the same for both the A20 and the Aerostar headset.
Also others could not hear him when he tried to communicate with other aircraft over radio. They said there was just noise transmitted.

As soon as I switched back to the Aerostar headset, everything was fine again.

After today's flights I tried to use my headset with a handheld radio and the quality of my transmission was good (both ways).

My first idea is an impedance- or level-mismatch; but I thought, all fixed-wing  aviation headsets had about the same impedance.
Are there ready-built circuits to adapt my headset to the intercom?

I really don't want to stick with the standard headset. Neither do I want to blow 1k€ on a Bose as I really like the H10.

Apart from it being a Becker I don't know anything about the radio in the plane but I've been told not to mess with the configuration of the radio, as it works in all other setups.

Edit:
After having found a datasheet for both the A20 and the H10-13.4 I'm more confused than before.

DC-Headset-Datasheet: http://www.davidclarkcompany.com/files/literature/10-13.4.pdf

A20-Datasheet: https://assets.bose.com/content/dam/Bose_DAM/Web/consumer_electronics/global/products/headphones/a20_aviation_headset_Orion/pdf/a20_hdst_PDF_ownersguide_EN.pdf

On page 38 of the A20's datasheet there is the technical data with the microphone output levels. It sais:

  Typical output is 600 mV at 114 dB SPL

The David Clark sais:

  Mic Sensitivity: 400mV+/-6dB into 150Ω load @ 1kHz for 114 dB SPL input

which seems to be tested under the same conditions. But the amplitude of the Bose is higher. Shouldn't the effect we have seen be the other way around? With his mic working and mine not activating the intercom? Or with him being very distorted due to clipping in the amplifier?
Hope someone knows better than me.

So after Juan's help and also talking to Becker I think I've found the answer:

It's an unlucky impedance combination.

That means maybe I can get it to work by lowering the VOX-level (increase mic bias) far enough so my instructor can activate it but if I lower it too much, my own mic will constantly activate the intercom, resulting in constant noise.

Becker told me, this is likely due to an old wiring version being installed where both pilot and copilot's mic are connected in parallel to the same amplifier. So when my mic has a 'better efficiency' i.e. better conversion from mechanical swing to voltage, the VOX adapts the threshold (or as Becker said the bias voltage for the mic) for this and the amplitude of the co's mic is to low to activate it.
A fix would at least require rewiring of the system to have dedicated amplifiers and bias supplies for both the pilot and co-pilot.

I think I confused some things in the physics here; if you point me to it, I will gladly correct it.

In general Becker's advise was to always use the same kind of headset for both pilot and all passengers in order to ensure best results (all volumes will be the same for all people then).


I just want to fly, so where do I go Ever since I was 10, I've always wanted to pilot an airplane by myself. I don't want to do it for the money I really just want live that "dream of flight" but where I grew up in a society that doesn't favor "dreams" or even flight. I really want to know, isn't there a place I could go and just fly without having to pay anything. To be honest, the fees at flight schools are really outrageous and discouraging. I want to know if there is a place in this world that I can just live that dream. By the way, sitting in passenger plane crowded with a bunch of people for several hours doesn't count at all. Please I hope that someone can help me.

If you join the military, dedicate years of your life to service, work hard, show skill and talent, and are lucky enough to be selected, they will train you to be a pilot and fly for free.  You will even earn a modest salary at it.

In the USA, the Army has more pilots than any other branch.
The Air Force, Navy, Marines and Coast Guard all have flight programs as well.


I want to be an airline pilot. Would becoming a NON-COMBAT Air Force pilot be a good way to become one? I know that becoming a fighter pilot is highly competitive, making it a difficult route, but would becoming a pilot for an Air Force cargo aircraft or something of the like be a good way to reach my final goal of piloting for an airline?

It depends on which part of the world you're in.

Airlines based in a country with a healthy General Aviation scene will probably prefer civil pilots. If there General Aviation scene is limited then it would make military pilots an attractive source.

I'm not saying that Military pilots are any worse/better but there have been airlines where the safety record was quite poor as a result of poor CRM from the military pilots, China Airlines and Korean Air are examples. These airlines have recognised and rectified the problems and today are up to industry levels in terms of accidents/incidents.


What does the phrase from the FAA, "clear to maneuver" mean? What, if anything, does the phrase, "clear to maneuver" mean if given by an FAA airspace controller?

That isn't standard FAA phraseology; at least, it isn't anywhere in the ATC orders. The closest thing is in section 9-2-20 on evasive action maneuvers. I know nothing about them, but they seem to be a military training thing:

  PHRASEOLOGY−
  CLEARED TO CONDUCT EVASIVE ACTION MANEUVER FROM (fix) TO
  (fix),
  and
  (number of miles) EITHER SIDE OF CENTERLINE,
  and
  MAINTAIN
  (altitude) THROUGH (altitude),
  and
  COMPLETE MANEUVER AT (fix) AT
  (altitude)

But of course both pilots and controllers use non-standard phraseology all the time, especially for unusual situations. It's certainly possible that a controller somewhere has indeed said "cleared to maneuver as requested" or something similar. Although the 'correct' phraseology would be "approved as requested" (see section 2-1-18 of the orders) for a general request.

Another possibility is that it's military phraseology, not civilian. If you can link to a source or ATC recording then you might get a better answer.


Why does Boeing use a trim wheel in the 737 and not their other products? Why does Boeing use a trim wheel in the 737 and not any other products?

Is the trimmed state for the 737 just more important than in the 777? Or even 747?

It gives the impression that a secondary control for the trim (If the power to the pitch trim motors have been cutout) is extremely vital, seeing it features two fold out handles that are located 90 degrees apart, so a pilot has good leverage at any point in the rotation to their desired trimmed state.

I take it that this style of a trim system is implemented in the 737 for a good reason, so I’m curious what makes this “style” the perfect fit.

On the 747, and 777 it almost seems that once power to the pitch trim motors have been cut-out, there isn’t a way to manually move the stabilizer? I’m very aware that I could also be 100% wrong, but why not have a trim wheel in all products? Or vice versa?

Trim pitch "wheels" as you describe date back to the time when turning that wheel actually pulled on steel cables that were connected to the hinge mechanism for the control surface itself. This mechanical/manual system was a simple and robust method of manually trimming the aircraft and was very widely used before electronic/fly-by-wire control systems were invented.

Since the 737 is the oldest basic design platform in the Boeing product line, its original design dates back to a time when trim wheels were mechanical and pilots were transitioning out of still older planes into Boeing's new offerings- and those pilots expected manual trim wheels.

It is likely that trim wheels in newer planes are a "legacy" feature, allowing pilots familiar with an older revision of the cockpit layout to transition to another newer plane in the design series.


Please explain differences between AFM and FCOM manuals? What are the key differences between AFM and FCOM and where they will be used?

The simple answer is that the AFM is a certification document whose content (procedures, limitations, and performance data) is fundamental to the airplane's certification requirements and is approved (both original and all revisions) by the regulating authority that certified the aircraft. You could say that the AFM is part of the airplane's type certificate.

The FCOM/AOM/Operating Data manual is just a company publication. Its content is not approved. It takes AFM procedures and expands them into a kind of company-recommended procedural framework, provides descriptive information, and provides non-certification related performance data used for planning, like cruise data, optimal profiles etc.


How is maximum payload determined in the payload-range diagram? What determines the maximum payload weight, as seen in the horizontal line of a payload-range diagram? I understand that

$ OEW + W_{fuel} + W_{payload} \leq MTOW$

but what's stopping me from just putting in 10lbs of fuel, enough to taxi across the apron, and therefore have a maximum payload weight of MTOW - OEW?

Aircraft also have a Maximum Zero-Fuel Weight (MZFW). This defines the aircraft's maximum weight without any fuel loaded. A large aircraft certainly would not be able to fly with only 10lb of fuel on board,
so structures like the fuselage are designed to carry a lower payload.

For example, the Boeing 777F freighter has a maximum takeoff weight of 347,814kg. The type certificate lists the MZFW as 248,115kg, which leaves almost 100,000kg for fuel out of the max fuel capacity of 145,538kg. This is a large increase from the passenger version (777-200LR), which has a MZFW of 209,106kg with only slightly lower MTOW.

See also: What are different types of weights of an aircraft?


What airframe design is best for stormy weather? Consider picking a plane for weather study. This plane will intentionally fly into weather systems (e.g. inside the eye of a hurricane) to collect scientific data. It will be equipped with on-board weather radar and other atmospheric sensors.

Which airframe designs are most suitable for this type of flying?

4 engines is probably a must for reliability
Piston? Turbo-prop? Turbo-fan?
Low wing? High wing?
Low / high aspect ratio?
Delta wing? Sweep wing?
Conventional tail? T tail?

You get the idea...

EDIT: I would also like to know why the current planes are chosen. For example, if delta wing is not used, then it suggests a certain criteria which cannot be met by the delta wing design (e.g. requires high AoA at low speeds).

In observing the configuration of the current aircraft used for weather study, it's important to also note that those planes were originally built for different missions that allowed modifications for such a special purpose.

The P-3 was built as a maritime patrol plane, which is a role not all that different from weather observation. It requires good range and endurance to allow the plane to fly out to sea and remain there long enough to accomplish its mission. The primary mission is using sensors, either onboard or deployed from the aircraft. The plane must also be able to withstand more time spent at lower altitudes and in more turbulence than typical aircraft.

The C-130 was built as a transport plane. This requires good range and payload capacity, both in weight and volume. These attributes have allowed it to serve in many roles, such as attack, special operations transport, and electronic warfare. As both aircraft were originally built for the military, they are built to withstand higher loading than typical civilian aircraft, which is useful when flying to bad weather.

4 engines are less efficient but provide redundancy - Both aircraft have 4 engines, as this is a good compromise between size of engine and propeller for this size of aircraft, at the time at which they were designed (around 1960). This primarily provides redundancy. The plane is required to be able to fly with one engine failed, and controllable with two on the same wing failed.

Turboprops are efficient at moderate speed - Both aircraft are also powered by turboprops. The primary roles for the aircraft do not require high speeds or altitudes, which is where turbofans have an advantage. Turboprops provide good power and efficiency at moderate speeds and altitudes, which is acceptable for shorter cargo missions and maritime patrols as well as weather observation. It's worth noting that the US Navy is replacing the P-3 with the P-8, which is a twin engine jet aircraft. A large part of this is likely due to the availability of an existing aircraft design, not being worth the cost of designing an entirely new plane. Although two engines provide less redundancy, they can still provide a similar level of reliability. Japan designed an entirely new maritime patrol plane, and opted for 4 turbofans. Although turbofans may require more fuel, they do allow higher speeds which allows the aircraft to reach its station faster.

Low wing may be a more versatile configuration - The high wing of the C-130 is mainly to allow easy loading and unloading of cargo by keeping the fuselage closer to the ground. This is less important for a weather observation role, though it does allow better downward visibility from the cabin. The P-3 sits higher above the ground, which allowed for a radar to be mounted underneath. Mounting sensors on top is certainly an option but may require modifications to retain stability. One might conclude that a low wing offers more versatility in this regard.

Moderate aspect ratio with sweep to match speed - The wing design will depend on the speeds for which the aircraft is designed. Low aspect ratios and high sweep or delta wings are good for reducing drag at higher speeds. There is no need for very high speeds in a weather observation aircraft, so these would seem to be poor choices. High aspect ratio and low sweep are good for reducing drag at lower speeds, which can maximize endurance. Though endurance is important for weather observation, these designs also have higher wing bending and generally lower top speeds. Both the C-130 and P-8 have moderate aspect ratios and low sweep, which offers a good compromise for strength and efficiency. Jet aircraft fly faster and generally use moderate sweep and aspect ratio.

Conventional tails can be more robust - T-tails have some issues with control and stability, and this prevents them from being used in most cases. The T-tail is mainly useful when the normal position of the horizontal stabilizer is taken up by engines or cargo doors, or would place it too close to wash the engines, or if efficiency is a high priority. Control and stability are particularly important when flying in adverse weather conditions, so if there is no other reason for having a T-tail, a conventional tail works better. All of the aircraft mentioned above have conventional tails.


Why is the JAC VOR an Initial Approach Fix for the KJAC VORDME Rwy 19 Approach? See the attached KJAC VOR/DME Rwy 19 approach.

QUESTION: Why is the JAC VOR an IAF for this approach?

There isn't a procedure turn to use this VOR as a functional IAF,
and the twin peaks (13,770' & 12,695' plus 7,139') should be enough to disuade you from trying while IMC.

The FAA Instrument flying handbook defines an IAF as:

Initial approach fix (IAF). The fix depicted on IAP charts
where the instrument approach procedure (IAP) begins unless
otherwise authorized by ATC.

The chart doesn't indicate radar contact required. I don't see any other route from the VOR JAC IAF to establish one's self on the final approach.
Hence the question on why the reason for labeling the JAC VOR as an IAF for this approach?

It's not an IAF according to the FAA approach plate:

Besides not being identified as an IAF, JAC could only be an IAF if there was a charted course reversal.  As the FAA approach plate specifically says "Procedure Turn NA" that possibility is ruled out.


Does navigation database provided by the database providers like Aeronavdata or Jeppesen consists of company routes? Does navigation database provided by the database providers like Aeronavdata or Jeppesen etc consists of company routes .

How is the company routes maintained are those modifiable by the OEMs ?
Is navigation database customizable ?

Any insight on this will be helpful.

The company routes are maintained by your company.  Some FMS installations have a computer program where you can create the company routes and upload them to each FMS.  Other FMS requires each FMS to be programmed.
All FMS have the ability to see if the routes have been changed due to a database change.   If the pilots wanted to use those company routes the FMS would require them to verify the routes are stored correctly.


What is aerodynamic damping? Could someone explain what aerodynamic damping exactly is? I'm not able to understand the whole concept. Pls try to keep the explanation simple.

I tried to understand the concept from the link below. Is aerodynamic damping the same as the dihedral effect, or is that a whole different story?

https://encyclopedia2.thefreedictionary.com/aerodynamic+damping

The link you provided has a poor choice of words: "restoring moment".

Damping forces are not restorative, i.e. they do not attempt to return the body to equilibrium, but rather oppose its movement. That is an important nuance.

Imagine a classic spring and dashpot vehicle suspension: the spring tries to restore the vehicle to its regular position, while the dashpot damps the velocity. By itself, the dampener will not restore equilibrium, it will stay at whatever position you extend it to, despite fighting the movement itself.

How does this apply to your question: aerodynamic damping is exactly that, the opposition  of the aircraft to rotation. You can observe it without flying: just imagine an aircraft hanging by its nose and tail, in such a manner that its CG is right between the supports. You can roll it by hand, but the drag on the wing will eventually stop this roll, but it will not level out the wings.

In flight, there are other forces at play that do provide a restoring moment, but aerodynamic damping does just what it says on the tin, it damps.


Why did the DC-3 have a much higher cruise speed than the HP.42, despite their similar weight and power? A review of the classic DC-3 and the Handley Page HP.42 yielded a surprisingly close match in empty and max gross take off weight at around 18,000 and 28,000 lbs for the HP.42 and 16,000 lbs and 25,000 for the DC-3.  The HP.42 cruised at 87 knots on around 4x500 hp, and the DC-3 at 180 knots on 2x1200 hp.  The HP.42 was a lower aspect biplane, the DC-3 a graceful mono plane, the epitome of aviation advances for that era but...

Questions:  How much of the DC-3's speed increase was the result of improved engine/prop efficiency?  How much from the DC-3's speed increase came from its beautiful Prandtl inspired wing?  How much from retracting its gear?  How much closer would the HP be with those improvements, while remaining a biplane (perhaps with improved struts)?

I do not expect an exact answer, I am more interested to see how the numbers were crunched and a short explanation why.  Thanks.

Struts every which way, uncowled engines, wheels with fenders hanging out, wires, bits sticking out here, bits sticking out there, corrugated skins, fabric wings and tail... it's a mess; a flying Truss Bridge.  There's just too much to try to quantify it like that.

You could probably take a DC-3 and start adding all those things one at a time, and each item would knock off 10-20 kt, and eventually you'd end up down at 87 kt, but the slower you get the smaller each accumulative penalty would be.


What is the minimum ceiling and visibility limits in Class E airspace? With the intention of landing, taking off, or entering the traffic pattern at an airport in Class E airspace, what is the minimum ceiling and visibility as a VFR pilot in the USA.

VFR cloud clearance requirements are listed in 14 CFR 91.155 and for Class E airspace specifies:

  Class E:
  Less than 10,000 feet MSL.
  Flight Visibility: 3 statute miles
  Distance From Clouds: 500 feet below, 1,000 feet above, 2,000 feet
  horizontal.

  At or above 10,000 feet MSL.
  Flight Visibility: 5 statute miles
  Distance From Clouds: 1,000 feet below, 1,000 feet above, 1 statute
  mile horizontal.

There is also a requirement specific to Class E surface areas that says that the ceiling must be at least 1,000 feet in order to operate in the airspace.  It is also listed in 91.155:

  (c) Except as provided in Sec. 91.157, no person may operate an
  aircraft beneath the ceiling under VFR within the lateral boundaries
  of controlled airspace designated to the surface for an airport when
  the ceiling is less than 1,000 feet.

Note that there are exceptions for both of these that refer to 91.157 Special VFR Weather Minimums if you are instrument rated and the aircraft is instrument equipped.


What 's the difference between Angle of Attack and Pitch? I am interested in knowing the theoretical and practical differences between the Angle of Attack (AoA) and Pitch:

Graphical definitions
How are they related?
In what circumstances these angles are equal?
While flying, do you need to consider both or only the Pitch?

Thanks in advance :)

The reference of pitch is the horizontal. The reference of AoA is the direction of the relative wind.


Has a passenger or cabin crew member ever flown an airliner? Is there any documented case, excluding hijacking, where a passenger or cabin crew member had to fly an airliner (hands on yoke/stick) – even if just briefly – due to an emergency (pilot incapacitation being the most likely one) in which he/she had to replace the pilot mid-flight ?

Aside from talk-down aircraft landings of small aircraft and stand-ins as Pilot Monitoring (which are both beyond the scope of this question), the only case I could find is:

Helios Airways Flight 522 where a flight attendant was spotted in the captain's seat shortly before the plane crashed

Do you know any other cases ?

I'm particularly interested in cases, in which the stand-in pilot was unqualified to fly this specific plane, but absent such cases all stand-ins as Pilot Flying in an airliner count.

I think that in United Airlines Flight 232 Dennis E. Fitch did. While flying as a passenger on this flight, he actually was a certified flight instructor for the plane of that type so competent.

Chances to find a type-rated ATP between the passengers who would fly as if nothing may look slim but they are not zero. It is statistically more probable to find a pilot between passengers than would be just by random chance, because of deadheading.


Do cabin evacuation tests include passengers with limited mobility? When doing the evacuation drills to ensure people can leave the plane in 90 seconds, are they tested with disabled people, ones in wheelchairs or, like myself, people who have difficulties walking and use crutches? I would never be able to jump on the slide or even evacuate in 90 seconds so what would that mean for me? Would I just be left behind?

As @mins said in the comments, the 90 seconds is a limit for a evacuation test. Having equal test requirements means that all planes have a minimum, similar evacuation capability.

That said, the conditions of an evacuation test are rather benign: people participating in them know nothing is really wrong, there are no hazards like smoke or fire, and the plane is in a normal attitude (no broken gear or hull, engines stopped). See

            .

In real emergencies, the time to evacuate may be greater than 90 seconds, and the crew and ultimately the captain has the responsibility to ensure that everyone has been evacuated safely and leave the ship the last. So, crew incapacitation left apart, you wouldn't be left behind.


Who's in charge of running VOLMET stations worldwide? Are the broadcasters private individuals, governments, companies? Are they required to function 24/7 and if they don't, are the owners fined?

This is an interesting question. According to the Air Navigation Plan of the ICAO (Part 6), all member countries have to broadcast these volmets, therefore it is extremely likely, that all Volmet stations are run by the government.

It also states that this service has to be available all the time, but I doubt that fines are involved. There will be a Notam issued though.

Source: http://aviadocs.net/icaodocs/Docs/9673_vol1_en.pdf


Are helicopter searchlights fixed or movable? Can the helicopter crew move the helicopter searchlights or are they always fixed at a specific location on the helicopter?

They are used by rescue helicopters mostly but I am not sure if crew can move them to look at specific area by some method or they are always fixed.

The question is some what unclear, but helicopters usually have some combination of 3 types of lights.

Landing light(s); fixed, sometimes pulsing, used for illuminating the area directly in front of and below the helicopter for landing.

Anti-collision light; fixed red and green and a strobe on the tail and sometimes the belly.

Search lights; directable, usually only used on military or para-public helicopters that fly at night. [SAR, Police, etc...]


How do civil aircraft flying in formation handle ATC? I assume that while en route, one aircraft could simply pick up flight following and the others do not need to talk to ATC, but what about upon reaching an airport? Do they simply announce "flight of xxx 10 mi east with W for full stop" and get successive landing clearances, or do they all break apart before getting close to the airport? Thanks!

As long as the aircraft are in formation, they are controlled as a single aircraft.
From US DoT OrderJO 7110.65T ATC General Control:

2-1-13. FORMATION FLIGHTS
a. Control formation flights as a single aircraft. When individual control is requested, issue advisory information which will assist the pilots in attaining separation. When pilot reports indicate separation has been established, issue control instructions as required.

The decision to break the flight lies with the pilot in command, and the ATC then controls the aircraft individually.

Separation responsibility between aircraft within the formation during transition to individual control rests with the pilots concerned until standard separation has been attained.

Upon break-up of the formation flight, the controller initiating the break-up shall ensure that all aircraft or flights are assigned their proper equipment suffix.


How are $V_r$ and $V_2$ determined? $V_r$ is the speed at pilot should initiate rotation on take-off and $V_2$ is the safe climb-out speed. Pilots determine them for each take-off by looking them up in a table in POH or QRH or somewhere.

But somebody had to fill those tables in using flight tests and calculations. What are the criteria by which the values are selected?

The limits of the $V_{r}$ and $V_{2}$ are determined by the regulations in place. The rotation speed is the speed at which the pilot can the aircraft rotation for take off even when one engine is inoperative.

Consequently, this speed should be more than the minimum control speed with one engine inoperative, $V_{MC}$. The current regulations stipulate that the $V_{r}$ should be at least 1.05 times $V_{MC}$.

The safe climb out speed or takeoff climb speed is the speed which the aircraft should have reached at a given altitude. As per FAA regulations, this height is 35 feet above the takeoff surface.

The climb out speed $V_{2}$ should be at least 20% greater than the stall speed $V_{s}$ and 10% greater than $V_{MC}$.

The FAA regulations prohibit lifting the nose landing gear before reaching $V_{r}$ and retracting it till the aircraft is completely airborne.

All aircrafts undergo these tests during their certification process and these data is used by the pilots. Another thing is that both $V_{r}$ and $V_{2}$ are given in terms of calibrated air speed.


What can I learn before I actually go to flight school (Austria)? I am currently occupied with a large project which basically eats up all my money but will be done in a year or so. After that, I would like to get my PPL. So I am currently out of money but do have some time left which I would like to use to already study the basics.

Is there any freely available material targeting PPL training? I live in Western Austria if that is of any concern (this is also where I would like to perform any training - LOIH is closest to my location).

Get hold of a simple simulator to familiarize yourself with the basics. I enjoyed Microsoft FSX . It's not intimidating. You can follow along just getting the basics, and you can hear generic pilot talk. It's not going to guarantee you a jump start hours wise, but at least when you get to flight school, you may have heard some of the terms and even messed with certain controls.

Don't expect to skip ahead without serious time investment. A few hours playing on a simulator(emphasis on PLAYING) will help with familiarity and maybe confidence, but be prepared to spend a lot of time listening to your instructor.

Another good thing, though it sounds silly could be to invest in some training videos. I personally enjoyed the courses offered by sporty's pilot shop. It was $200 when I bought it, but I would argue that it paid for itself, since I needed less time paying instructors and renting planes to practice things.

On the other hand, sometimes you hear instructors say they prefer blank slates as opposed to people coming in with bad habits. Maybe be patient and wait until your instruction begins. That way you start off with the habits that your specific school likes to train.

Good luck!


Can an ARINC 429 controller set to receive messages on high-speed (100kHz) see 12.5kHz messages? I am working with an ARINC 429 controller which is currently set to receive messages at 100kHz. When the transmission line sends messages that are 12.5kHz (standard ARINC 429 low speed) the controller can see them.

Is this normal for an ARINC 429 controller?

That is normal for an ARINC 429 receiver. The clocking for ARINC 429 is built into the transmission data, with the bipolar Return to Zero format having a Null for the last half of each bit time and requiring 4 bit times of null (0) voltage between labels. This lets the receiver adjust to the data rate automatically.


Wing moment - providing stability or not It is said that wing alone is unstable, because it provides a nose up moment, so tailplane is needed to damp it. But normally wing provides a pitch down moment (as far as I know, apart from very high aoa situation) because centre of pressure is behind the centre of gravity. So shouldn’t wing moment be actually stabilising? I’m confused about stability, because we one time we consider stationar lift acting in aerodynamic centre and moving centre of gravity, next time moving centre of pressure with stationary centre of gravity and so on... please help me out.

It's not about the moment but its change with AoA.
Any wing can be trimmed when the cg is at the center of pressure. What counts is how things change when AoA changes.
If you want stable behavior, use an inverted airfoil. A regular, cambered airfoil will cause unstable behavior.
For a trimmed airplane the moment around the center of gravity is zero. Now it is important how this moment changes when the airplane moves away from this trim point. If AoA increases and the moment becomes negative (nose down), the airplane is stable.
If the center of gravity is too much forward, the airplane cannot be trimmed in the first place because control authority is insufficient to produce enough downforce at the tail in order to compensate for the pitch-down moment of the lift force on the wing around the more forward center of gravity.


How might one start a new logbook for an engine that had one lost? About 6 months ago in a hangar at a local (KLWT), I saw a Piper PA-30 Twin Comanche and instantly wanted it. When I got home, I did a look up on the Registration (N) number and found out that the aircraft was de-registered in 2005.

I did some asking around the airport the next day and discovered that the owner had passed away. After some more research, I discovered that the airplane had one engine and its prop totaled. It had the propeller and engine replaced, but neither had logbooks and that was why the plane is collecting dust.

I really would like the airplane, because it is actually in good condition, yet it sits in the back of the central hangar and is ignored by everyone. So in a nutshell, the airplane is in good condition with airframe, avionics and logbooks for the right engine and prop. There are just no left prop or engine books.

The current owners (the estate of the deceased pilot) do not seem to even realize that the airplane is still sitting there, so I do not think that they would put much thought into selling the plane and I might be able to pick it up relatively cheaply. The only thing that I seem to need is a logbook. So I was wondering if it would be possible to somehow just start a new log after purchase? The other option is to just buy a new engine with books. Any advice?

One way to get a new engine logbook is to send the engine for a factory overhaul.

Your engine will be regarded as a usable core, and will come back with all tolerances within "as new" limits and a new logbook.


What are the advantages and disadvantages of an oblique wing over a swing wing? This question asks about the benefits of an oblique wing over a delta wing, but I am more interested in the benefits of an oblique wing compared to a swing wing.

Wikipedia states:

  This is a variation on the classic swing-wing design, intended to simplify construction and retain the center of gravity as the sweep angle is changed.

But I'm pretty sure there are a lot more advantages or disadvantages, in terms of stalling behavior (forward swept side inboard first, aft swept side outboard first), aircraft control etc.

Related: What are the advantages of a forward-swept wing over a rearward-swept wing?

The oblique wing and the swing wing aim to reduce the drag over a wide range of speeds by changing the wing sweep. While the swing wing rotates a part of the wing to achieve this, the oblique wing rotates the whole wing.

The first production aircraft with variable sweep wings was the F111 Aardvark, while the most famous one is the F-14 Tomcat.

"F-14 Tomcat prototypes in flight c1972" by U.S. Navy - U.S. Navy National Museum of Naval Aviation photo No. 2011.003.301.027. Licensed under Public Domain via Commons.

However, the only full sized aircraft to be produced with an oblique or pivot wing was the NASA AD-1, which was strictly an experimental aircraft.

"AD-1 ObliqueWing 60deg 19800701" by NASA - http://www1.dfrc.nasa.gov/Gallery/Photo/AD-1/HTML/ECN-15846.html. Licensed under Public Domain via Commons.

A comparison between the two can be made like this:

Aerodynamics: The oblique wing is much more refined aerodynamically compared to the swing wing and had lesser drag. In fact the AD-1 was designed to be as close to the optimal for all the flight regimes. Also, the aircraft was designed to have an elliptical lift distribution to reduce induced drag. on the other hand, the variable geometry aircraft did not offer any significant advantages over fixed wing baseline aircraft.

However, the asymmetric stall of the oblique wing aircraft would cause problems as one side of the wing is swept forwards and the other side is swept towards the rear.

Structure: The hinge was arguably the most critical structural part in variable sweep wing aircraft. The hinge should not only have a very high reliability, but also have the capacity to bear the high aerodynamic loads.

"Tornado variable sweep wing Manching" by Sovxx - Own work. Licensed under CC BY-SA 3.0 via Commons.

In this case, the swing wing aircraft are better off compared to the oblique wing aircraft as the amount of load on the hinge is significantly lower.

For example, the oblique wing hinge has to take not only the weight of the entire aircraft wing (the swing wing aircraft typically rotate only a part of the wing), but also the entire fuel load (the amount of fuel carried in the variable part of the wing is significantly small). Also, the hinge should take the load of the control system too.

Handling and Controls: The handling of the swing wing aircraft have been brought closer to the fixed wing aircraft over time. However,the handling qualities of AD-1 was found to be poor, with unusual trim requirements and inertial coupling affecting the aircraft negatively.

For instance, the AD-1 required about 10° of bank in order to trim the aircraft with no sideslip at 60° wing sweep.The aircraft also experienced pitch-roll coupling and the associated aeroelastic effects made for unpleasant handling qualities above 45 degrees sweep.

One advantage of the oblique wing aircraft is that the center of lift and mass doesn't move as the wings are swept. This happens in the swing wing aircraft and the control system is complicated

Engine and payload In case of swing wing aircraft, the engines can be mounted in the fuselage (like F-14) or in the (fixed part of) wing itself (like B-1). In case of the oblique wing aircraft, locating the engines anywhere except the fuselage is effectively ruled out.

In case of military aircraft, use of hardpoints in the variable point of the wing is limited (for one thing, this will increase the load on the hinge). This is a much more serious problem for oblique wing aircraft as this limits the payload that could be carried.

However, the main reason for the lack of further development of oblique wing aircraft is their unusual and unpleasant control qualities.


Why don't plane wings start at the front of a plane and end at the back? This is what some people think the SR 72 will look like.

If a plane wing was attached to the whole fuselage, couldn't it have a shorter wing span? If it had a shorter wingspan it would be less of a lever so could be less strong and therefore lighter. I don't mean a blended wing.

You are right, a short wing span is a blessing for the structural design and the wing will be nice and light. But since you need a certain wing area to keep the aircraft in the air, the wing will have a long chord as well, and that won't be good for aerodynamic resistance.

For subsonic aircraft, you want the longest, narrowest wing possible: the lift create by the wing is caused by air accelerating downwards. The amount of air streaming in is a function of the span, so a long span accelerates a lot of air downwards only a little bit; a short span wing has to accelerate much less air much more. That creates induced drag: the horizontal component of the backwards tilted lift vector.

Another source of drag is the tip vortex, where air 'flips over' from high pressure below to low pressure on top of the wing. So for subsonic aircraft, the longest, narrowest wing is the most beneficial from an aerodynamics standpoint. It will add constructional weight and therefore increase weight induced drag, but will compensate for it by a reduction in aerodynamic induced drag.

Supersonic aircraft have an additional source of drag: shock waves. The air gets no warning that an aircraft appraches. The nose arrives first, and a shock wave streams off of the nose in the form of a cone. Inside the cone, the air has lower velocity - if the wing can stay within the cone, it creates much less supersonic drag.

Image source

The higher the supersonic speed, the more the shock cone bends backwards, and the widest bit of the wing needs to be more towards aft to remain within it. So for supersonic aircraft, the delta wings that you draw are in use. They create a relatively huge drag when flying subsonic though.


What design features or systems help to prevent a hard nose landing? Pilots perform perfect manual landings almost all the time with the nose wheel touching down softly and elegantly. When landing an aircraft of any size really more so for the jumbos and super jumbos, this seems like an incredible feat given their weight and the speed at touchdown.

Apart from training, what design features or systems aid the pilot in achieving a soft nose wheel touchdown? Are there any features to help pilots in the event of an accidental abrupt push of the yoke during touchdown?

The longitudinal stability of the aircraft.

Aircraft are designed so that at any given elevator position they maintain a corresponding angle of attack¹. Any decrease in AoA creates pitch up moment to increase it and vice versa.

At touch down the pitching moments change a bit, but the general tendency remains, so without change in the elevator position, the plane will tend to keep the nose wheel off the ground. The nose only touches down when the pilot eases the back pressure on the control column, or the plane slows down enough that the elevator efficiency decreases below what is needed to keep the attitude.

The pilot just has to ease the back pressure gently and not slam on the brakes until the nose wheel is on the ground, because brakes do generate significant downward pitching moment (this applies to all vehicles; you can feel it in a car quite well).

¹ except modern fighters, but there the control computer emulates that behaviour, otherwise they wouldn't be controllable.


What is "judgemental oversteering" in taxi procedures? I found a phrase that I don't understand while reading Jeppesen charts: "judgemental oversteering".

I found it in general information about taxi procedures. As I understand this procedure applies only to jumbo aircraft because it takes place only if the wingspan is more than 118ft (according to the chart which I read).

Can you explain to me what is it? What kind of conditions can require this procedure? Examples or images would be appreciated.

"Judgmental oversteering" means to intentionally not follow the taxiway centerline when turning. It is a technique used on large aircraft to turn on tighter or smaller taxiways.

In a sense, it is like driving a long vehicle, such as a truck or a bus. Instead of following the lines on the road, the driver would deliberately overshoot the entry of turn, i.e. delay turning the steering wheel. This technique allows the rear wheels to stay on the road instead of going over the corner which may have fences, poles, pedestrians or other obstructions.

Here is a drawing from the 747x Quiet Longer Range Family Airport Compatibility document which illustrates the tracks of each gear for the "judgmental oversteering" and "cockpit centerline" methods:

This FAA document about airport design summarizes the pros and cons for each method (p.52 of PDF, p. 34 of document):

  Cockpit Over Centerline. Taxiway intersections designed to accommodate cockpit over centerline steering require more pavement, but enable more rapid movement of traffic with minimal risk of aircraft excursions from the pavement surface. (...)

  Judgmental Oversteering. Taxiway intersections designed to accommodate the judgmental oversteering method of maneuvering require the least pavement widening. However, judgmental oversteering requires complex maneuvering, increases the risk of aircraft excursions from the pavement surface, and slows the flow of traffic.


What was enabling control to the pilot on the Snecma C-450 Coléoptère? Looking at the Snecma C-450 Coléoptère, I was wondering about the (4?) fins towards its tail:

Source: Wikipedia

Were they able to pivot to help the pilot control the aircraft?
If not, what else was enabling control to the pilot ?

Great find, a vehicle with so many new design features in a time before Computed Fluid Dynamics, and hard to test in a wind tunnel where the device could only be mounted in a fixed position.

From this source:

  Takeoff, hover, and landing were controlled by deflecting vanes in the engine exhaust: in horizontal flight by four fins mounted just above the castoring landing gear, and in the transition to vertical flight by two retractable canards in the nose.

This source states that the four delta surfaces were movable and were to be used to control horizontal flight. They were puny though, and mounted quite close to the aircraft roll axis. One of the problems encountered during test flight was a slow uncontrolled roll.

  For the control of the aircraft in fast flight, there were four cast solid control surfaces allowing in-depth aerodynamic control (horizontal control surfaces) or in rolling and direction (vertical control surfaces). For the phases of vertical takeoff and landing, control was ensured by deviation of the jet (pitching and lace) and of compressed air coming from the compressor (rolling).

The same source has a frontal view of the craft:

So yes the four delta surfaces were able to pivot but were obviously inadequate for providing any control at low speeds. Thrust vectoring was required for slow flight.


Are military and jet pilots given any extra training before entering commercial aviation if yes, then how? Because a jet pilot is habitual of flying super sonic aircraft, which can possibly go in any direction and do many maneuvers, which commercial aircraft can't, are they given any special training before entering commercial aviation?

Watch out for the words "centerline thrust only"!

The overall answer to your question depends on the military pilot's background and experience.  Military heavy jet pilots (bomber and transport) will have very little difficulty converting over to civil airliners, as civil airliners and military transports of equivalent role are close cousins in flight characteristics, and many bombers aren't that far off either.

Fast-jet pilots, however, can run into one specific difficulty when transferring to civil jet aircraft.  Most (albeit not all) twin-engine tactical jets have their engines mounted very close to the aircraft centerline.  This means that there is very little yaw when an engine fails in a tactical jet, which is quite difference from the response of an airliner, or even most light twins, during an engine failure.

Hence, a pilot whose sole multi-engine experience is in twin-engine tactical jets may receive a "centerline thrust only" restriction on the CPL/AMEL certificate they are issued on the basis of their military experience.  This restriction must be lifted before they can fly or receive a type rating in a non-centerline-thrust aircraft (even a DC-9 yaws enough on engine failure not to count).  Thankfully, it's not a hard restriction to lift -- in the worst case, it's simply a matter of passing the multi-engine checkride in a light twin with wing-mounted engines, and may be liftable as part of a type rating course for a non-centerline-thrust multi-engine aircraft for that matter.


Why does the cockpit have windows, is it a structural design burden? Instead of cockpit windows could they have just screens displaying what is happening using a camera? Is it for any useful purpose? Is it a structural burden or is it there for psychological purposes?

Yeah, it may be better. But what happens if the camera gets dirt (as everything else does in a flight) or if the camera fails for whatever reason? If the aircraft suffered an electrical malfunction and the camera was to turn off? Also, this is way more expensive than just fitting the window. The technology would also increase the weight of the aircraft. It's a good idea that I am sure that aircraft manufacturers have contemplated. It is just too impractical.


What happens when an aircraft type is grounded while in flight? Over the past few days, many countries have decided to ground the 737 MAX. Among these, several have also decided to deny passage to the affected models through that country's airspace. How does this affect flights which were already in the air at the time of the announcement, typically? I can see several options:

The flight returns to its origin, fuel permitting
The flight lands at the closest viable airport in the destination country if fuel is insufficient for a return to origin (minimizing the amount of time in the destination country's airspace)
The flight proceeds to its destination airport as filed, even if this means spending several more hours in the destination country's airspace than the second option
The flight proceeds to the closest viable airport regardless of whether that airport is in some third country being overflown (although I can foresee this causing immigration/visa/customs issues for the passengers)

I'm assuming that (1) is commonly used, given the flight paths on internet flight trackers yesterday, but which of the other options are rooted in reality?

The FAA is currently dealing with that on the 737 MAX.  They are allowing any airborne 737 MAX to continue to its destination or to an alternat or emergency landing site at the discretion of the crew  within the US thence flight ops are prohibited. Special airworthiness certificates and ferry flight permits may be issued by the FAA for moving the aircraft to a home base or maintenance depot as the discretion of the Administrator.


Why was the Boeing SST numbered "2707"? Boeing worked its Supersonic Transport (Boeing SST 2707) design in the 1960s. They gave it the number "2707". Why was this aircraft given that number? Did it have some significant inside-Boeing relation to the B707 or was it just some number that followed another Boeing numbering scheme?

The planned cruise speed was Mach 2.7 so I always assumed 2707 was a combination of Mach 2.7 and the then current Boeing 707.


Which languages are EASA exams and other documents available in? Does EASA provide exams, documents and regulations only in English or in all the European Union Languages?

For example, I have to attend an exam for an EASA license. Can I do it only in English, or can I use another European Union language?

This post is an answer to the original question:

  Which is EASA official language? English or all European Union Languages?

EASA communicates in English. They facilitate the translation of regulations to all member languages, but ultimately these translations are not within their domain of responsibility.

Therefore the official language appears to be English only.

See https://www.easa.europa.eu/the-agency/faqs/regulations:

  Implementing Rules are available in all of the national languages of the EASA Member States. How is the quality of these translations assured? Who is responsible for the translations?

  EASA is committed to facilitating the production of good quality translations. To ensure this and, where necessary, to improve, EASA has set up a Translation Working Group in 2008. This Working Group is made up of members of the National Aviation Authorities (NAAs), the Translation Centre of the EU Bodies (CdT), as well as EASA staff members. Also, EASA in cooperation with NAAs and CdT, is developing glossaries in the different aviation domains, such as Air Operations or Air Traffic Management, to enhance the quality of translations. The Member States also contribute to this project in order to capitalise on existing material and experience.

  The final responsibility for translations lies with the EU Commission. The correction of translation mistakes of the Implementing Rules follows the same formal procedure as for their adoption: 1. preparation of the proposal, 2. interservice consultation, 3. committee, 4. scrutiny of European Parliament and of European Council, and 5. adoption. For minor mistakes, the procedure may be shorter. In any case, the linguistic changes will have to be agreed by the Commission’s translation services. These linguistic services will check that no substantial change is introduced, that the term used is acceptable according to an internal translation code or that the same change is included in all linguistic versions.

And here https://www.easa.europa.eu/the-agency/faqs/recruitment:

  What language should I use in my application for a post at the Agency?

  Applicants may use any of the official languages of the European Union when applying for a post advertised by the Agency. However, in order to speed up the selection process and to reduce the amount of the translations needed, applicants are invited to use English. Nevertheless, applicants will not be disadvantaged in any way even if they use other official languages of the European Union.

  [...]

  What language should I use in my application for a traineeship/study placement at the Agency?

  A very good knowledge of the English language is an essential requirement to do a traineeship/study placement at EASA. Applications must therefore be submitted in English. For the same reason, the documents concerning traineeships and study placements at EASA are only available in English.


Does waverider have much lower drag than Sears Haack body? I tried to calculate drag for hyper velocity project using this paper for Sears Haack revolution body. Some parameters:

Diameter: 160mm (round number for simulating 155mm projectile)

Fineness ratio: 13.2, which means projectile's length is 2112mm

From the paper, the assumed wing area $S$ is

$$0.077 \cdot l^2 = 0.077 \cdot (2.112)^2 = 0.3435 \ [m^2]$$

From the Figure 15 in the paper, the total Cd at 2km/s is about 0.004

So total drag at sea level
$$D = 0.5 \cdot v^2 \cdot \rho \cdot S \cdot C_D$$

$$D = 0.5 \cdot 2000^2 \cdot 1.23 \cdot 0.3435 \cdot 0.004 = 3380 \ [N]$$

From the paper, the volume $V$ of the projectile is

$$V = 0.002655 \cdot l^3 = 0.025 \ [m^3]$$
Assume it is filled with aluminum, then the mass $m$ is about
$$ 0.025 \cdot 3000 = 75 \ [kg]$$

So the drag is about 4.5g.

On the other hand, there is an empirical formula for hypersonic lift to drag ratio is:

$$\frac{L}{D} = \frac{4 \cdot (M + 3)}{M} = \frac{4 \cdot (6 + 3)}{6} = 6$$

It seems that if the projectile is shaped as a good waverider then drag can be as low as 1/6 of its weight, assuming the waverider is the best shape for hypersonic lift to drag ratio.

There is of course the problem about scaling where mass is increased at cubed speed, while area only increases at squared speed. While I don't have an complete computational model of waverider to compare directly with SH body, but it seems at the first glance, the waverider can get much lower drag than even the most aerodynamic shape, 1/6g vs 4.5g.

So is it true that the waverider has much lower drag than a SH body?

A waverider will prevent the compressed air under the airframe from escaping sideways. An equivalent view is that the sideways component of the air displaced by the body is used for lift creation by straightening it and pushing it down at the wingtips. This allows it to fly at a lower angle of attack for the same lift, which reduces supersonic lift-related drag linearly with the reduction in angle of attack.

The drag of a Sears-Haack body is the lowest for a given volume and a given fineness ratio. Increasing the fineness (essentially, the local inclination times the circumference of each body section) will reduce drag. This increased fineness, however, will now cause less sideways displacement of airflow which could be used for the waverider effect.

In the end, the question as asked is not answerable. What can be said is:

A blunt Sears-Haack body will profit the most from the waverider effect.
A waverider is still a Sears-Haack body if it has the right cross section distribution over length.
A waverider will maybe lower drag by 20% or 30% in a realistic configuration and at Mach numbers between Mach 3 to 5.

The empirical equation for the L/D of a waverider looks suspicious. Without knowing the constraints of its validity, I would not trust its results. Also, the drag coefficient of your Sears-Haack body looks like the zero-lift drag. You might need to add the lift-related drag to arrive at the complete drag.

And the biggest mistake is to operate it at ground level - 2000 m/s would be appropriate in 30 km altitude. Get the drag figure there and you will arrive at a much lower drag just by operating it in the appropriate density.


How does one determine runway orientation without a local wind rose? We are planning to establish new airport, but then we have no wind rose analysis of the location.

How can we predict what's the right orientation for the runway that satisfies the 95.

Assuming that you are not bound by local topography and thus can build the runway in, theoretically any direction you like, there are a few things you can do. First, you could set up a small weather station and record some data. You could then use this data to determine your direction. You can also use a site like this one to see the historical wind/weather data in the area. This will help you get an idea of the prevailing winds at near by.


How is wind measured at this small U.S. airport? While launching gliders at Front Royal, VA (KFRR) over the weekend, a fellow pilot and I got curious about the airport's weather equipment.  We know that KFRR has local equipment to measure wind speed and direction. There is a screen in the FBO that shows a graphical readout of the wind situation.  However, it was not obvious looking at the equipment itself how this is done.

Here are two pictures I took:

Nothing on either of these two pieces of equipment was actively spinning or being visibly affected by the wind.  At the time we has a 10-12 knot headwind almost directly down the runway.  This equipment is ~40 feet to the left of the runway threshold.

Question: Is one of the pieces of equipment I've photographed responsible for measuring wind speed? If so, how?

Ultrasonic anemometers are replacing the traditional cup anemometers in automated weather stations.  The sensor measures the time it takes for an ultrasonic pulse to travel between the probes, which is affected by wind speed. In your second image, the object directly above the lights appears to be an anemometer.

Source

Ultrasonic sensors have the advantage of no moving parts and lower maintenance requirements. Also, with additional probes, they can measure the wind in 3D.


What if you don't recognise an aircraft ATC is telling you about? Often an ATS will warn you about other aircraft: when you're taxying and need to give way, or for land-after (and other conditional) clearances, or to warn of traffic in the area you're flying in. Usually they do this by naming the type of the traffic, and often you need to positively confirm whether you have the traffic in sight. For example:-

  "G-ABCD, report departing Squirrel in sight"
  "Affirm, traffic in sight, G-ABCD."
  "G-ABCD, behind the Squirrel, cross runway 18 behind, report vacated."
  "Behind the Squirrel, cross runway 18, wilco, G-ABCD."

What if the type of aircraft you're warned about is one you don't know? In an area with lots of vintage or experimental aircraft, you might not even know whether to look for a fixed-wing or a helo. I wouldn't want to say I have the traffic in sight if there's a risk I'm not looking at the same aircraft.

  "G-ABCD, report departing Squirrel in sight"
  "The what? Is there wildlife on the runway? G-ABCD"

Is there a standard way to explain the situation and disambiguate? Failing that, is there a concise way that will not be misunderstood over noisy radios?

(For the benefit of other readers who wouldn't recognise a Squirrel: it's a helicopter, and the local police operate one out of Cambridge. It was the first obscure-sounding aircraft name I could think of to use as an example.)

To add to Dave's answer, if traffic is pointed out to you which you are unfamiliar with, ask for clarification. ATC or FIS will have a good understanding of aircraft types and speeds, especially in radar environments the speed will be available as groundspeed (GS).

  FIS: DELFF, traffic information, 3 o'clock, 4 miles, same altitude, Mooney Bravo, passing right to left.
  PIC: DELFF, unfamiliar with aircraft type.
  FIS: DELFF, traffic is a low wing aircraft, 100kt groundspeed


How should I log time when I fly from one airport to another and back again without landing? How should you log flight time when flying from airport A to airport B and return to airport A without landing at airport B?

The time from when you started the engine to when you stopped the engine.  It doesn't matter where you went, except for where you specifically need to record the trip details for training requirements purposes, or for your own historical record.  So you'd log the overall trip time, startup to shutdown, adding something like, "CC YYY to XXX back to YYY - no landing at XXX" in the Remarks.


What is the usual practice in interacting with ATC at Top-of-Descent? Presuming an ordinary long-haul flight on which the plane's navigation system has selected a point as Top-of-Descent, and there are no particular issues (such as weather), when would ATC typically be contacted?  That is, would the pilots seek to obtain ATC clearance for descent in advance of reaching TOD so that they could start down at exactly that point?  Would the pilots cross TOD and then call ATC to ask for clearance?  Would there be a point when the pilots get early clearance to descend once the TOD point is reached but wait awhile to hit the TOD point?

There are some variances in the way a pilot/crew may handle the initiation of a descent (at or near the TOD point as described in your question).  My answers below reflect my preferences based on normal circumstances. (IFR Jet operations in U.S.)

  when would ATC typically be contacted? That is, would the pilots seek to obtain ATC clearance for descent in advance of reaching TOD so that they could start down at exactly that point?

If I had not received a descent clearance when approaching (a couple of miles before) the displayed TOD I would request a descent clearance from ATC. This would help avoid being too high and perhaps struggling to meet some published altitude restrictions (e.g. if on a STAR, etc.).

  Would the pilots cross TOD and then call ATC to ask for clearance?

I would not wait until I'm past the TOD (typically) to ask for a descent clearance - see the answer above.

  Would there be a point when the pilots get early clearance to descend once the TOD point is reached but wait awhile to hit the TOD point?

(I'm not entirely certain I fully understand this question) - Prior to reaching the TOD, ATC may issue a "pilot's discretion" descent clearance (e.g., "descend at pilot's discretion, maintain flight level 210"). Then I could wait until the TOD point (displayed on my nav equipment) to start my descent.  Or I might get a "descend via" clearance on a STAR (Standard Terminal Arrival procedure) which would authorize a descent to comply with the STAR profile, and based on where I was, I could wait to start the descent at my discretion (as long as I comply with the STAR profile).


Why do new jet engines cost billions to design? This question might come off as crude because it involves people's salaries, but I do not understand why new designs of large turbofans cost many billions of dollars to design. For example, the Pratt & Whitney geared turbofan apparently cost 10 billion USD.

Why? Last I checked, most scientists and engineers do not make millionaire salaries. I think it's more around 100 to 250k tops. Even if you had 100 of them working for 10 years on it, that would be 250M, or a quarter of a billion dollars. Instead, jet engine designs seem to cost multi-billions.

I don't understand. If it's just designing a jet engine, then raw materials cannot possibly be a major factor even if it's something like titanium or composites. How many prototypes could you possibly need? I mean I hope it's not all trial and error.

The other thing is computer software, which I thought would make things easier and cheaper to design. Granted you cannot just input the desired thrust and press a button, but surely there is decent fluid dynamic software out there that can help you design something much easier and faster than before.

So what makes it so expensive? Is there some super costly certification process? Or do you somehow need more than 100 engineers collaborating? 1,000? 10,000? If so, why? Cannot imagine that.

Maybe someone can explain the general process of jet engine design in the first place because I'm sure that would be helpful. They way I imagine it, you just go through stage by stage and try to get each blade shape and diameter right.

Or maybe I have some misunderstanding and the 10 billion includes the costs to put up the factory?

Even if we ignore the salaries of everyone involved; engineers, sales people, management, Q/A teams, manufacturing teams, more sales people, and then a few spare engineers...

  I don't understand. If it's just designing a jet engine, then raw
  materials cannot possibly be a major factor even if it's something
  like titanium or composites.

While the raw materials alone are not necessarily costly, the materials, as well as the machining and processing, can be quite costly. This can be further compounded if the engine uses some kind of new material for which there is no effective production method yet. This was the case for the entire production of the SR-71 Blackbird which needed to figure out how to work with titanium before actually building anything. Even once the bespoke parts are produced for a new engine the company will then need to figure out how to produce the parts in sufficient quantity to produce the engines for market.

  How many prototypes could you possibly need? I mean I hope it's not
  all trial and error.

It's not, but the FAA may require various demonstrations where they destroy the engine and you can bet the manufacturer is going to try that out before running any official tests. Once passed initial tests flying prototypes will need to be built and tested on real airframes that cost money, running jet fuel that costs money.

  The other thing is computer software, which I thought would make
  things easier and cheaper to design. Granted you cannot just input the
  desired thrust and press a button, but surely there is decent fluid
  dynamic software out there that can help you design something much
  easier and faster than before.

It makes some things faster, like FEM, and surely makes complex routing easier, but like a good wrench, CAD software is a tool that makes things faster and easier. It does not do the work for you.


How to calculate lift and drag coeffecients for VTOL aircraft in the takeoff stage? How would I calculate CL and CD for a VTOL aircraft while it is in it's takeoff/landing stage?

The particular aircraft is a fixed wing/quadcopter hybrid so I know that I can treat this as a thin rectangular plate problem. However, because the aircraft takes off vertically, I do not understand what formulas to use to calculate these coefficients.

If I use CL=2$\pi$$\alpha$, where $\alpha$=$\pi$/2, then I end up with CL=9.87, which just doesn't make sense.

At $\alpha$=$\pi$/2 the flat plate is perpendicular to the air stream.

CL is defined as the force perpendicular to airstream, CD as the force in direction of the air stream. When the craft takes off vertically, its CD is high and its CL is zero.

A graph and a most excellent explanation here


Is there a maximum length for NOTAM? I see some very long NOTAM messages describing a whole section of arrival or departing procedure.

Is there a standard limiting how long a NOTAM can be? In computing I usually see limits in bytes, is there such a limit on NOTAM?

According to an FAA guide to creating NOTAMs (see pages 14 and 21), the "condition text", i.e. the body of the NOTAM...

  has a max length around 1200 alpha-numeric characters. If necessary,
  the system will allow a user to create up to ten parts with 1200
  characters each

But, that doesn't include other parts of the NOTAM, like location, date/time, graphical elements etc. I don't know if there's a limit (in kB?) for the complete NOTAM file or not; the document doesn't seem to mention anything about that. It also isn't clear from the FAA document if the ~12,000 characters is a format limitation/specification, or a tool limitation.


Are some airline's flights more noisy than others for security reasons? LHR has published a table ranking the noise and pollution levels of the different airlines using the airport. At the bottom of the list is Israel's El Al.

El Al, in their official statement, say that this is because they are using older 747-400 planes which are due to be replaced by Dreamliners. However, somebody was trying to explain to me that the extra noise was due to particular flight methods and manoeuvres which they implement for purposes of security and defence, being a high risk airline.

I'm not sure what they could do differently, especially as they should be under UK ATC control.

Does anyone have any concrete knowledge (obviously not classified info) or an educated guess whether this guy's theory is rational or not.

Being familiar with neither El Al nor LHR, what follows is entirely in the category of "educated guesses".

There are two broad ranges where noise levels can be affected by operations, those being on approach and on departure.  The things that tend to make aircraft noisy on approach would be configuring early and flying down final with lots of drag (i.e. full flaps) and lots of power (i.e. lots of engine noise).  On departure, using maximum thrust instead of a reduced thrust takeoff tends to be more noise close-in to the airport, but it results in a steeper climbout, which makes for less noise farther away.

Would "standard operating procedures" for a "high risk" airline tend to require either of these?  Hard to say.  As far as survivability, configuring early means that if you take a missile close in, you're already in a landing configuration, so losing a hydraulic system or two doesn't affect your ability to get configured for landing.  On the other hand, being at full flaps makes performance on a go-around worse if you take the missile and can't change configuration (but need to go around rather than land).  Plus, engines running at the higher power setting would tend to be more of a target for an IR (heat-seeking) missile.  If you thought you were coming in to a high-threat airfield, you'd probably want a steep approach, meaning lots of drag but a LOW power setting.  I have a hard time envisioning a 747 doing this coming into LHR, but maybe they do, spooling the power WAY up to arrest the steep descent at some point close-in.  Maybe.

On departure, the max-thrust takeoff DOES get you out of some threat envelopes more quickly than the reduced thrust takeoff, so that's fairly believable.  Get as high as you can before you depart the airport perimeter (which is presumably more secure than the areas outside the airport fence).  If "always fly a max thrust takeoff" is part of the El Al S.O.P., then it wouldn't be surprising that this would result in higher noise levels close in.

Still in the "educated guess" category, I would wonder if some element of the noise ratings may have to do with how they're calculated.  If the rating for British Airways averages out the 747's departing at heavy weights to destinations far away (four engines at very high power settings putting out lots of noise) with smaller, lighter airplanes departing to closer destinations (two engines at reduced thrust, putting out less noise), then their average would be lower than a carrier which is always flying heavy 4-engine jets to a fairly distant destination.  Not that El Al would be the only airline in this situation, I'd suspect, but not having smaller & less noisy aircraft to reduce the average may be at least one factor in the ratings.

Without seeing the actual ratings and at least some of the methodology as to how they're calculated (near/far, approach/departure/both, weighted by time of day, whatever else), it's very hard to know what's really going on there.  Plus, taking a look at the procedures into LHR & seeing if there is any difference in how El Al flies them and how "everybody else" does.  A lot of questions there in order to get a true high-quality answer to what's really driving those results.


Is there a way to find out which runway is used by which flight on a particular day/date? For example, i want to know which runway was used by NH 829 that flies from NRT to BOM (Narita-Tokyo to Bombay-Mumbai)

For flight tracking, I know and use these websites/apps - FlightAware, FlightRadar, FlightStats, Aviability, FlightMapper, Planefinder and Kvikr.

https://www.flightradar24.com/data/flights/nh829
https://flightaware.com/live/flight/ANA829
https://www.flightstats.com/v2/flight-tracker/NH/829
https://planefinder.net/data/flight/NH829
https://www.flightera.net/flight/All+Nippon+Airways/NH829
https://info.flightmapper.net/flight/ANA_NH_829
https://www.radarbox24.com/data/flights/NH829
https://www.airportia.com/flights/nh829/tokyo/mumbai/
https://www.planemapper.com/flights/NH829
https://kvikr.com/flight/nh829_ana

But none of them provide information about runway used for takeoff or landing at the source or destination airports respectively. I am looking for a publicly accessible, preferably free to use website/smartphone app/API or even a historical dataset (recent flights not those from the previous decade)

Is such information kept a secret (intentionally) or is it just that no one displays it, probably stored in the database. I understand that realtime information may not be available, but for past flights, such data should be available. I guess there could be country-specific restrictions too. But i want to see as much public data for any flight as available.

My ultimate goal is to find out which runway is used by LH717/LH716 and QF25/QF26 for takeoff and landing at HND (Haneda-Tokyo), so that i can get a better view of the Boeing 747 from as close as possible.

(Guessing the) Runway Selection

For spotting airplanes, you want to know which are the current active runways. The runway history of planes or flights shouldn't matter much, unless your plane of interest is limited in what runways it can use.

Large airports have many parallel runways. In general, outsiders will not have enough information at hand to predict the active runways. The factors that are considered for the selection of active runways are the following:

  Aircraft take-off and land into the wind, or with minimal tail wind.
  Based on the wind direction, air traffic control will decide which
  runway is to be used at any given time.

  Larger airports tend to have more than one runway, so that a runway is
  always available depending on the wind direction. Airports with just
  one runway are generally constructed so that the runway is aligned
  with the prevailing wind.

  Runway selection is monitored at all times, as weather conditions can
  quickly change. Every runway has a wind indicator known as an
  ‘anemometer’, and wind observations contribute to the runway selection
  decision. Pilot reports of upper level winds can also impact on runway
  selection.

  When a runway is selected, it needs to be available for an extended
  period of time to allow pilots to plan their descent, approach and
  landing. As this involves anticipation of developing trends, aircraft
  may continue to land on a runway for a period when weather conditions
  at a local level no longer appear to warrant it.

  Other factors that air traffic control will take into consideration
  when deciding which runway to use include:

  the number and type of aircraft programmed for the airport
  length of runway(s)
  weather conditions (both present and forecast); including wind velocity and gradient, wind shear, wake turbulence effects and
  position of the sun
  availability of approach aids in poor visibility conditions
  location of other aircraft
  taxiing distances, including availability of taxiways
  braking conditions.

  Some airports also have ‘preferred runway’ systems. This means that if
  wind conditions, workload and traffic conditions permit, a particular
  runway will be used to move traffic as efficiently as possible to
  reduce the noise impact over residential areas.

This text is quoted from a short informational document on runway selection published by Airservices Australia.

ATC radio communication

It is possible to listen to ATC radio communications with a handheld scanner (always check if this is legal in your country!), or via the internet (LiveATC). There are different channels including Departure, Approach, Ground, and ATIS.

ATIS

Busy airports are usually equipped with Automatic Terminal Information Service. ATIS continuously broadcasts relevant information about the airport and immediate surroundings for pilots. This includes the actual runway in use. One can receive ATIS via VHF, or via phone. Frequencies and phone numbers are published in different ways. Airnav.com might be useful for the USA. LiveATC provides streaming of ATIS.

Ground

Aircraft are cleared for taxi to a runway on the Ground channel.

Approach

Aircraft receive their instructions and clearance for a runway on the Approach channel.

Websites

Airports

Some airports are publishing their actual active runways on a website. For instance:

Amsterdam (Schiphol): "Baangebruik Schiphol".

This airport always assigns 1 active runway for landing and 1 active runway for starting. In the rush times, it opens an additional runway for landing or starting. In the snapshot above, the 2 runways for landing are red, the single runway for starting is blue.

Brussels: Runways in use

There are probably not that many airports publishing this information to non-pilots, but surely there are more. Please comment if you know any other!

Flight Tracking

If there is no information available from the airport directly, you can always use flight tracking web sites like the ones you have listed in your question to observe which are the current active runways, for starting and for landing respectively. Keeping in mind that the assignment of active runways is not random, it is always reasonable to guess that the next aircraft will use the same runway as the previous ones. For approaching aircraft it is often possible to see if it is directly pointing to a runway, or if it follows a pattern to a runway that other aircraft have taken before.

Standard patterns and Operational procedures

If interested and willing to dig a bit deeper, you can always find and study standard approach patterns and operational procedures of your airport, e.g.

Operational Procedures at Tokyo International Airport (Haneda)
search the internet for "RJTT SID STAR"

In combination with flight tracking web sites, this will allow you to recognize the usual patterns, and predict earlier where a tracked plane is going to land.


What are these engineers doing sitting on a large format drawing of B-47s aircraft? This answer about solid-jet-assisted takeoff links to the page B-47 Jet-Assisted Take Off (JATO). An image there took me to a collection of historical aviation images, apparently from a LIFE Magazine archive.

Browsing there led me to the image below, of what looks like several aviation engineers sitting on a very large format drawing of a B-47 aircraft and its major components.

A reverse image search leads mostly to sites written in Russian, which I can't read.

Does anyone recognize what's actually happening here? It's not scene one would normally see these days.

source: http://images.google.com/hosted/life/2ce91e390933d837.html

  B-47 Stratojet Bomber, Date taken: September 9, 1950 Photographer: Howard Sochurek

As commented by Anilv, they are examining a factory production layout/plan. They most likely are attempting to resolve a production or supply problem, though as Anilv suggests, they may also be planning the factory layout.

Listed below is an example of the B-17 Flying Fortress Factory Production Layout used by Boeing in WWII. Note the arrows which show the production procession and parts/sub-assembly entry and exit.

Source - Boeing


What is the definition of “blade scatter” in gas turbine compressor dynamic balancing? Can someone help me define “blade scatter” gas turbine compressor dynamic balancing?

I assume there is an ellipsis somewhere in your source text, meaning the intended interpretation is "blade weight scatter", which does make sense in the context of dynamic balancing.

The meaning should be self-explanatory: the distribution of weights among nominally-equal turbo-machinery blades, which is important to keep the inertia tensor of the assembly as diagonal as possible when using the usual axis.


How does the noise of a 2-to-4-seat helicopter compare with that of a similarly-sized fixed-wing aircraft? We are considering allowing helicopters on our private airstrip (2600 ft strip). Noise on the ground (and approach) is the concern from the community.

Does anyone know approximate dB ratings for a typical 2-4 seat helicopter vs. a 2-4 seat fixed-wing propeller aircraft? I know there is no exact comparison, but just an approximation would be helpful.

I found one study comparing helicopter and airplane noise levels and signatures:
Aircraft source noise measurement studies summary of measurements...

Unfortunately this study does not provide conclusions or any  abbreviated comparison in plain language (or I just failed to notice them). It does, however, provide a near endless array of tables to shuffle though and compare.

According to the study there are similarities and differences in noise signatures between helicopters and airplanes, especially depending on the phase of flight and this hardly comes as a surprise.  In real life the biggest problem arises form the differences in how people react to sounds. Some of us might not care much about even the loudest jet noise (I, for example live a couple of miles form an AFB, and I don't mind), and some experience the slightest noise as a terrible nuisance.

What I would recommend, based on my very limited (but still academic) studies on acoustics, is to conduct a series of test flights and measurements to:

verify that legal (if any apply) decibel limits are not exceeded
give you measurement data for comparison and later reference
and, most importantly, to give you and the area residents an idea of the noise related to helicopter operation.

It should be noted that noise charts, such as those presented in the study above, are not easy to interpret. Decibel is a rather tricky unit, and does not necessarily correlate with the way one experiences noise. In comparison, for example, helicopters might be louder in decibels in some stages of flight than same size airplanes, but the noise might not be experienced any more disturbing (or pleasing, depending on how one is inclined)

Human ears are by no means precision instruments, and actually neither are high end decibel meters: their accuracy is typically somewhere in the range of 1 decibel, and considering it equates a difference of 26% in sound energy, and 3 decibels would be doubling or halving the sound energy, it's not very precise... To make things more complicated, an increase of 1 dB is just barely noticeable by human ear (or brain). 3 dB is perceived as about a quarter louder, and 10 dB feels twice as loud.

So: there's not much to distill from decibel charts or measurements unless the differences are huge across the whole frequency range (more than 10 dB), and even then it's still somewhat ambivalent... It's best to get real life experiences when it comes to sounds.


How does one launch unmanned high-altitude balloons without posing a safety risk to aviation? How can people launch balloons privately (filled with helium or hydrogen) that reach the altitude of 30,000 feet? Isn't that a safety risk in the same way as geese?

Unmanned balloons can indeed create a safety risk for aircraft. An aircraft could collide with the balloon itself (as described in the case that Jan Hudec posted in his comment), or with the balloon's payload (see the FAA's AIM section 7-5-4 for general comments on this).

But it's important to note that unmanned balloons are (or should be) launched only after appropriate preparation and communication; most countries have some sort of regulations to follow. In the US (for example), 14 CFR 101 governs unmanned balloon launches and it includes the following requirements:

Launches must be in (mostly) clear skies and away from airports and built-up areas
The balloon must have a radar reflector and lights (if launched at night)
ATC must be informed in advance of the balloon launch, expected path etc.
The operator must track the balloon's position and descent and report them to ATC as needed

In other words, the balloon should be as visible as possible - both visually and on radar - and ATC should know where it is. That gives pilots a way to see and avoid the balloon and ATC can provide warnings and/or avoidance instructions to aircraft directly where possible, which is actually fairly similar to how aircraft avoid other aircraft.

Of course, there may be cases where someone launches a balloon without following those rules (or the local equivalents in another country). That would create a much higher safety risk but it would be illegal and the operator would be risking penalties for doing it.


What measures prevent a military aircraft's weapons from being fired on the ground? Recently the 20mm cannon of an F-16 was accidentally fired on the ground by maintenance personnel at Florennes Air Base in Belgium, resulting the the destruction of another F-16 and damage to a third.

https://theaviationist.com/2018/10/14/f-16-completely-destroyed-by-another-f-16-after-mechanic-accidentally-fires-cannon-on-the-ground-in-belgium/

What measures do  military aircraft have to prevent their weapons from being fired while the plane is on ground?

Normally with aircraft there is a sensor called a weight on wheels switch.  This tells the computer that the aircraft is on the ground.  The computer (or a system of relays for older air frames) will prevent any system that was designated by the owner, or required by regulations, from activating while in the ground.  Also as a secondary preventative measure certain mechanical systems are also pinned in place after landing to help prevent ground actuation.  However if it happened during maintenance it is very likely these systems were disabled to perform system maintenance on the cannon.


Is it possible for an indirect (Russian) attitude indicator to work in 3D without tumbling? For a reference of direct and indirect attitude indicator, see How is a confusion possible between Western and Russian Attitude Indicators?, and https://www.skybrary.aero/index.php/Western_and_Russian_Artificial_Horizon_Formats.
Direct (Western) attitude indicators can be made to work without tumbling, or even made into a "Navball" that also displays directional information:

See the attitude indicator at the center, Source, and Source.
Or alternatively, look at Kerbal Space Program's navball.
Is the same thing possible with the indirect style indicator?
If one plays DCS, he or she should know that this style of indicator would always tumble when maneuvering pass 90 degrees above horizon, even though the gyro has no gimbal limit.
This is understandable, because otherwise the indicator must display the horizon upside down... or am I missing something?
Is there another way I missed which can get around this issue, or is indirect attitude indicators not capable of representing full 3D orientation, like a navball can?

Yes. It's actually easier.
Just consider the fact that an indirect indicator consists of two separate moving parts with one degree of freedom each, rather than one with two (or even three for navball) DoF. Instead of a ball, the pitch indicator can be a ring with continuous rotation, like so:

Note that most modern attitude indicators have a remote (separate) sensor, with the indicator driven mechanically by little servos (like the pictured AGD-1) or, of course, rendered digitally. This makes things even easier: the gimbal lock is a separate problem of the sensor (avoided with a tracking mechanism, pictured on the left here), while indication can be made however we want. You can easily have continuous pitch as well as continuous roll.
However, this is usually not done (on either type of indication), and this is a matter of convention rather than technical limitations. If we allow unrestrained angles, attitude becomes ambiguous: pitch ±180° with zero roll is the same as pitch 0 with ±180° roll. For this reason, the convention is that pitch is limited to ±90°, so only the second of these indications is valid. The necessary consequence is that roll "tumbles" when going past ±90° pitch. At the same time, the pitch indicator just inverts direction (and so mechanically it can be a semi-circle).
As a result, you will consistently see 180° roll, zero pitch no matter how you arrive to it: by a semi-loop or by rolling. This is reasonable given that continuous rolling is much more common.


How does a helicopter pilot execute an auto-rotation landing? What are the critical steps a pilot follows to perform an auto-rotation landing?

I am going to assume that by "critical", you mean survivable.  I will also assume that the engine failure occurs at a height which will kill you.
It's not so much critical steps, it's critical outcomes.  The single most critical outcome is to preserve, or regain, rotor RPM.  What steps are needed to do this will depend on what the aircraft is doing when the engine quits and, to a lesser extent, the type of the helicopter.  I will generalise for an "average" helicopter in straight and level flight.
The immediate action that is drilled into everyone from the very earliest hours as a student is to lower the collective.  Doing this has three effects.  It removes the positive pitch from the blades which removes most of the drag, it aligns the rotor thrust vector with the axis of rotor rotation therefore not using rotor energy for anything except lift and it causes a clutch to disengage the rotor from the engine allowing it to freewheel.  From this point onwards, you are heading back towards earth.
The second immediate action at the same time as lowering the collective (assuming forward flight) is to pull back on the cyclic to flare.  This loads the disc which causes it to "cone" upwards which reduces the disc diameter.  Therefore, the centre of gravity of the disc moves inwards and due to conservation of angular momentum, the rotor RPM increases.  For quite complex reasons, the nose of the helicopter will also pitch down when the collective is lowered so pulling back counters that tendency.
The third immediate action is to push in the pedal on the opposite side to the rotation of the blades. If the blades rotate counter clockwise (to the left as the pilot sees it) you push in right pedal to reduce the thrust which is produced by the tail rotor which is no longer countering the yaw caused by the drag from the powered rotor.  This is less critical than the first two and although it can be dangerous and get you into an uncomfortable attitude, it is usually possible to recover from not pushing the pedal in immediately.  If you've got rotor RPM, then you can sort it out.
Now you have successfully entered autorotation.  From here, fly more or less normally to the next critical point which is about 50' off the ground.
What you've done is to ensure that the rotor has flying RPM and that you are managing energy by trading potential energy (height) for kinetic energy (rotor RPM).  The conversion is done by the airflow which now comes from under the disc and "drives" the rotor to maintain RPM.  The pitch is neutral, or maybe even negative but, the relative airflow is now upwards through the disc and therefore, the blades have a positive angle of attack and generate some lift.  This stops the helicopter from falling.  There is some drag generated as a consequence of generating that lift, but it is easily overcome by the power which is now driving the rotor from that upward airflow.
As long as you are descending, that conversion will happen and your RPM will be maintained.  The controls are rigged such that with the collective fully down, RPM will remain in the normal range.  Sometimes you have to tweak it a little with small amounts of collective, flares and turns but in general, you just fly towards your landing spot.  The allowed RPM range is greater in autorotation.  For example (and from memory), the R22 has a range of 97-103% in normal flight and 90-110% in autorotation.
You are now descending with a high rate of descent and usually, significant forward speed.  You need to reduce both of those to get to a safe arrival. To do this, there are three more critical steps.
Starting at about 50 feet (depending on lots of factors but let's stick with the average helicopter which entered autorotation from straight and level with significant altitude), you flare the aircraft by pulling back on the cyclic.  This will immediately begin to slow the aircraft.  It will also begin to increase RPM (you are now converting speed into rotor kinetic energy).
At the same time, you increase collective to reduce the rate of descent by increasing the lift generated.  This will rapidly increase the drag, but now the energy needed to maintain the RPM is coming from the flare which is converting speed into RPM.  You also need to put in pedal to stop the aircraft from yawing as the drag increases on the rotor.
Providing you get the entry right and your flare reduces the speed and rate of descent to something survivable, then you will walk away.  You might wreck the helicopter and break some bones, but arrive at 10 feet with only 20 knots and 150 feet per minute rate and you'll get away with it.
If you are well trained and in practice, then you will land safely and smoothly with no damage to  machine or people.
In summary, critical steps:

Entry.  Lever down, cyclic back, pedal in.
Arrival.  Cyclic back, lever up, pedal in.