How do aviation engineers ensure that the landing gear opens every time, without fail? This is mostly with respect to large commercial airliners. I mean so many things can go wrong, then how have the engineers designed it to make it fail-safe? Or is it a very simple trick.

Also, are there any new developments in this area of landing gear, like lighter gear, or fixed gear etc.

The short answer is extensive testing and backup/manual over ride systems. In reality there is not a whole lot that can go wrong, landing gear systems are fairly simple in design.

This varies a bit by airframe but most landing gear systems are pretty much the same. Basically every aircraft out there, from a single engine Piper Retract all the way up through a 747 has some form of manual gear over ride system. You can read about that in this answer here. So basically if the main system fails (and it happens) they have some kind of manual over ride to force the gear down. Granted there can be cases where the manual over ride also does not bring the gear down but you can only be so redundant. Some gear is also held in place positively, in other words there is pressure on the system holding it up so that should the hydrolics fail you dont need the pressure to get the gear down. Often the gear is oriented so that gravity and aerodynamics can deploy it.

Fixed gear is generally not a great idea on anything bigger than a small trainer. Fixed gear adds drag at the cost of a simpler airplane. You can read up on a similar question here.

I dont think lighter gear is something they are looking into to solve the gear deploy issue. Generally speaking you want the gear to fall down in the event of a failure so a little extra weight is not the end of the world.


How will radar systems be used in FAA's NextGen ATC plans? Based on the reading I've been doing of FAA's Next Generation Air Traffic Control (NextGen) plans, I've been wondering if and how radar systems will continue to be used for ATC as NextGen rolls out?

Questions include:

Is it correct to assert that radar coverage will effectively become a less precise, backup only, data feed? I am suggesting this because my understanding (which could easily be incorrect) is that ADS-B will mandated for most (everyone?) and so aircraft will be actively reporting their precise position without the need for a radar track.
Will existing radar coverage eventually be phased out?  Seems unlikely due to airspace security issues alone. But are there any other reasons to keep radar coverage?

Under the ADS-B rule of the FAA aircraft operating in Classes A, B, and C airspace, as well as certain other specified classes of airspace
within the U.S. National Airspace System are required to operate ADS-B Out avionics.

This means that these aircraft can be tracked without the use of radar. These ADS-B tracks will be more accurate than radar tracks and have a higher update rate. However for reasons of integrity, continuity of service and security, radar will continue to provide coverage. Currently a lot of airspace is covered by multiple radar layers, the introduction of ADS-B allows for a reduction in redundant radar coverage.

Aircraft not equipped with ADS-B (operating outside of class A,B, or C airspace) will be tracked using radar. The radar tracks will be broadcast on TIS-B (Traffic Information Service - Broadcast) so that aircraft with ADS-B In receivers detect these aircraft as well.


What regulations exist for ATC real time RADAR simulator software? Does professional ATC RADAR simulator software need to comply to some regulations or requirements in order to be used for real life controller training?

Have ICAO, Eurocontrol, EASA or FAA published any such regulations or requirements in their documents? If so, any reference to a document is appreciated.

So according to EASA, it is the AMCs/GM for Regulation 2015/340, Part ATCO.OR (Annex III to Decision 2015/10/R) and specifically in AMC1.ATCO.OR.C015(b)(b) where is specifies 11 criteria regarding STD standards, among them being accuracy of aircraft performance, voice recognition realism, equipment, data displays, etc:

  STD criteria

  If  a  synthetic  training  device  (STD)  is  used  for  training, it should
  be approved by the competent authority as part of the course approval process
  for  any  training  plan.  Training  organisations  should  demonstrate  how  the STD  will  provide  adequate  support  for the  intended training,  in  particular, how  the  STD  will  meet  the  stated  objectives  of  the  practical  training exercises and enable the performance objectives to be assessed to the level determined in the training programme.

  This  demonstration  and  the  related  documentation  should  include  the
  following relevant criteria:

  (1) the  general  environment,  which  should  provide  an  environment  in
  which  STD  exercises  may  be  run  without  undue  interference  from unrelated activities;

  (2) the STD layout;

  (3) the equipment provided;

  (4) the  display  presentation,  functionality,  and  updating  of operational information;

  (5) data displays, including strip displays, where appropriate;

  (6) coordination facilities;

  (7) aircraft   performance   characteristics,   including   the   availability   of manoeuvres,   e.g.   holding   or instrumental landing system   (ILS) operation, required for a particular simulation;

  (8) the availability of real-time changes during an exercise;

  (9) the  processes  by  which  the  training  organisation can be assured that staff associated with the training conducted with the use of an STD are
  competent;

  (10) the degree of realism of any voice recognition system associated with
  the STD;

  (11) where  a  simulator  is  an  integral  part  of  an  operational  ATC
  system, the  processes  by  which  the  training  organisation  is  assured  that interference  between  the  simulated  and  operational  environments  is prevented.

  The  extent  to  which  the  STD  achieves  the above criteria  will  be  used  to determine  the  adequacy  of  the  STD  for  the  proposed  use.  As  a  general principle,  the  greater  the  degree  of  replication  of  the  operational  position being  represented  the  greater  the  use  will  be  possible  for  any  particular training.


Why is it that T-tails want to climb like on a PA-44? It seems like it always wants to climb I'm having a little difficulty understanding the aerodynamics of a t-tail and how it affects climb.

Because of the location of the horizontal stabilizer, it isn't as affected by the power setting. Thus, it's likely that you are trimming to compensate for power reductions when you don't need to. I would make sure you trim well, and ensure you are trimming based on what the airplane needs rather than what you would put in on a Cessna.


What does Hawaii ATC do in the case of ICBM warnings? Recently somebody pushed the wrong button when testing the ICBM warning system in Hawaii and set off an ICBM warning statewide for 45 minutes.

In all probability ATC would ground departing flights and possibly local ones, but what about inbound flights? Were they ordered to turn back? Continued inbound? What is the procedure for dealing with such a warning?

Here's an account that NATCA shared on their facebook page:

Veteran Honolulu Control Facility (HCF) member Steve Olson, recounting the experience of working yesterday:
“8:07am I was plugged in working airplanes like I do every Saturday morning, when the day took a turn into the surreal. Pilot after pilot started to check in with the same question. ‘Center, can you confirm the missile launch?’
“Then, as questions on the control floor were asked, it seemed like every phone in the room started ringing. The word ‘confirmed’ stung like a knife in the gut. As I started to advise the pilots on frequency that the missile launch is confirmed, the frequencies grew silent.
“As I did the only thing I could, continue to take care of the planes in my charge, all I could do was think about the ones I love, my loving wife and amazing kids. With less then 10 minutes there was nothing I could do.
“We found out rather quickly that it was a false alarm, but it seemed like forever.
“With my heart racing and my stomach in my throat, this is what was in my mind. Every day, for the last 29 years, when I leave home for work I hug Meagan, kiss her and tell her I love her. It may sound silly and trite, but today, for 10 long minutes, it mattered.
“Don’t take anything or anyone for granted.”


How do I do these VOR time and distance calculations? I'm trying to figure out the calculation to these questions:

  A pilot tracking a VOR turns 90 degrees from current heading. The
  pilot notes that it takes 3.0 minutes for the plane to intercept the
  radial 5 degrees from where it previously was. What is the time to
  VOR?

And:

  Using the previous question, what is the aircraft speed if the
  distance to travel is 100 miles?

I used the formulas my professor gave me and the numbers are coming out unrealistic to me. Could someone walk me through how to get the correct answer?

Here is the formula you are looking for:
(You can use this formula to answer your first question. I'm not entirely clear on what the second question means.)

Here is a nice discussion of the time/distance check from the Flight Learnings website: time/distance to station


Where are the fuel tank sumps on an Aquila A210? When I drain the fuel I have to do it three times:

  In addition to the drainer openings on both undersides of the wing and under the front fuselage (3 times in total).

Can you tell or show me where the third drainer (under the front fuselage) is located. Do you have a picture of it?

The third drain is at the bottom of the electric fuel pump;  The AT01 is what Aquila calls the AT210 on their web site.


Are there any companies that use atom interferometers in aircraft? Are there any companies that use atom interferometers in aircraft? If so, are they used for navigation? If not, is it possible to assemble it?

Here is the link from wiki Atom interferometer and link from MIT Technology Review of it and a link from a company work on it.

Probably not.

The 2012 paper Advances in Atomic Gyroscopes: A View from Inertial Navigation Applications* states in the abstract that "there are still lots of problems that need to be overcome to meet the requirements of inertial navigation systems." Even once atomic inferometer gyroscopes are able to meet the basic requirements of inertial navigation systems, it will take years of testing and certification before they will actually be used in production aircraft.

I highly suggest reading that paper if atomic physics is your thing, but for us the conclusion is gold:

  Recent progress on atomic gyroscopes has demonstrated that AIG is an
  ultra-high precision gyroscope for strategic grade inertial navigation
  in the future, and ASG is a high performance gyroscope which features
  both high precision and compact size. There are still lots of problems
  that need to be overcome when considering the atomic gyroscope for
  inertial navigation applications, however with the technologies
  available in the near future, the AIG could be used in space for
  fundamental physics research, the ASG based on comagnetometer can be
  used in strategic grade gimbaled INS, and the navigation grade ASG
  based on NMR can be demonstrated on chip-scale size. Furthermore, with
  the development of new theories and technologies for atomic
  manipulation, the future of high performance inertial navigation
  applications using AIG and ASG is indeed bright.

I would be slightly more cynical about time scales than this paper. This intro to INS notes on page 5 that it took 18 years for ring laser systems to reach maturity. No current atomic gyroscope system can meet the performance of ring laser systems, and the highest-performance AIG systems are on the order of a cubic meter. Chip-scale ASG systems have been produced, but their performance is dreadful compared to mechanical or ring laser systems.

*Note: I'm not sure how much to trust this article. It's published in a peer-reviewed journal, but there are clear copyediting errors. I don't have a better source, though, so I'll trust it for the purposes of this question. Also, note that this paper does not only have aviation users in mind; there are a lot of references to strategic INS, which I think refers to submarines, and it also talks about INS in the context of satellites.


Does the FAA intend to discontinue domestic flight plans and switch to ICAO-only on October 1, 2015? According to someone on the internet, the FAA intends to discontinue accepting domestic flight plans and switch to ICAO-only in October.  I've also heard this around the airport, but been unable to verify it.

The provided link says that the FAA is proposing to phase out domestic plans, but doesn't say that they've committed to it, nor does it give a date.

  The FAA is also proposing to implement flight plan filing for civil
  aircraft exclusively under the format used by the International Civil
  Aviation Organization (ICAO).

Is there an official FAA publication that verifies the FAA's intent to stop accepting domestic flight plans on October 1, 2015?

The link from your question paraphrases and links to “Flight Service Program Changes,” of which the April 13, 2015 7:49:56 AM EDT revision is reproduced below with added emphasis in boldface.

  Flight Service Program Changes

  Recognizing a shift in users’ preferences for automated services, the
  FAA is changing its Flight Service operation to make it more efficient
  and reduce costs. The agency will continue to maintain the highest
  level of safety.

  The changes come as general aviation pilots are transitioning from
  traditional Flight Service assistance to more automated and web-based
  tools to obtain services. Through the use of updated technology Flight
  Service is taking the opportunity to eliminate redundancies and
  underutilized services.

  “None of these changes will affect core flight service safety
  functions such as search and rescue, emergency services, Notice to
  Airmen (NOTAM) entry and dissemination, and pilot weather reports,”
  said Steven Villanueva, Deputy Director Flight Service, in the ATO's
  System Operations Service Unit. “We are phasing in the changes to ease
  the transition for users,” he added.

  On October 1, 2015, the FAA will consolidate Flight Watch services
  into routine flight services inflight frequencies to eliminate
  unnecessary duplication of service and provide greater convenience for
  pilots. These services provide inflight weather information to pilots.
  After that date, these services will be available on the same
  frequencies that pilots use to open and close flight plans and to
  receive updates on NOTAMs or Temporary Flight Restrictions (TFRs).
  Dedicated Flight Watch frequencies will be decommissioned.

  The FAA is proposing to phase out legacy Remote Airport Advisory
  Service. Seven of the airports do not meet the Agency's criteria for
  receiving advisory service. Flight Service is collaborating with our
  user groups on possible impacts and will be posting the proposed
  change in the Federal Register for public comment.

  The FAA is also proposing to implement flight plan filing for civil
  aircraft exclusively under the format used by the International Civil
  Aviation Organization (ICAO). Flight plans contain specific
  information relating to the proposed flight of an aircraft and
  controllers use them to provide air traffic services. Today pilots
  file flight plans in the U.S. under either the domestic or ICAO
  format. The use of one format will simplify the process and align U.S.
  flight plans within ICAO standards.

  General aviation pilots increasingly have turned to automation in
  recent years to file flight plans and receive pre-flight briefings.
  New technology such as ADS-B is providing more inflight options to
  pilots. Flight Service will incorporate the industry's newest
  technologies and reduce or eliminate other functions to create
  efficiencies and value. The changes to Flight Watch and RAA are the
  first in what is anticipated to be a series of right-sizing
  initiatives surrounding flight services provided to pilots.

  Send your comments, questions, and suggestions to us and share your
  thoughts and ideas.

  Flight Service National Airspace Initiative (FSNI) Frequently Asked
  Questions (FAQ)

The linked FAQ list contains a question similar to yours, quoted below including the boldface from the original. Note the first sub-bullet under Flight Plan Filing that states the intent but does not provide a specific date.

  What changes will be made in the Long Term?

  Long term changes are being worked with stakeholders. Increased usage
  of technology and automation and less reliance on human delivered
  services will be considered. These changes include:

  Emergency Frequencies — Pilots, when in distress and using an emergency frequency (121.5MHz), will be responded to by an Air Traffic
  Control (ATC) specialist with surveillance capability, improving the
  timeliness of emergency handling.
  Flight Plan Filing

  Increased automation that will provide a pilot numerous alternatives for flight plan filing, modification, activation and closure
  Transition to exclusive International Civil Aviation Organization (ICAO) format for civil aircraft

  Search And Rescue (SAR) — Increase automation to include Automated Activation and Closure of flight plans
  Relaying Instrument Flight Rules (IFR) Clearances — Flight Service is working with Air Traffic Control (ATC) to develop alternative solutions to enable pilots to talk directly to an air traffic control facility when requesting an IFR clearance.

See also the related Aviation.SE question Will the frequency 122.000 MHz no longer be used for Flight Watch after October 1st 2015?


What is the difference between a concourse and a pier? Both are narrow buildings with aircraft parked on both sides, so what is the main difference?

(image source)

In terminal designs, the main difference between a pier and a concourse is that a pier is connected by terminal buildings on one side, but a concourse has separate terminal buildings connected by transportation either under or over ground.

In practice, the terms "terminal" and "concourse" are often used interchangeably, with "satellite" being used in that specific case, and "piers" being referred to as terminals or concourses.

Simple

Small terminal with a few gates.

Linear

Longer than a simple terminal, with gates on one side. May be curved or straight.

Concourses

Standard terminal with gates on one side, with additional linear terminals connected underground or by buses (occasionally by a bridge), each with gates all around. Each is generally designated as a different concourse.

Standard

A main terminal area, with long extensions having gates down one side. May be designated into different terminals depending on the size.

Pier

Like concourses, extensions with gates down both sides, but connected on one end by additional buildings. Each pier may be designated as a separate terminal.

Satellite

A main terminal area connected to one or more smaller terminal buildings with gates all around. Generally connected underground, occasionally by a bridge. Each satellite is generally designated a different terminal.


Can wing clouds caused by a high angle of attack be recreated in a lab? Also, why doesn't this work for smaller wings (e.g. r/c planes) Can this be recreated in a lab? Any equations would be helpful if so. Also, why doesn't this happen during high angles of attack on a smaller wing, such as that of an R/C plane?

The sudden fog due to the fast (and hence adiabatic) expansion of air is re-created, in many laboratories, in the simple cloud chamber.

For those that haven't seen one (they are fast disappearing from school labs due to 'radiation risk'): it is a small, usually round chamber with a window. Inside, there's a a small amount of water to ensure a water-vapor saturated air. As the chamber is closed, the water is in stable equilibrium with its vapor. The chamber is connected to a hand pump that resembles a bicycle pump, but working in reverse. When you pull the pump handle, you make a partial vacuum in the chamber, and due to the sudden descent in pressure, the temperature drops too, and some of the water vapor inside the chamber condenses. If the pull is light enough, the condensation will take place only along the trajectory of the alpha- or beta particles emitted by a suitable source placed inside. But if you pull hard enough, the whole chamber fills with fog.


How does one train for making landings and takeoffs in bad weather? I thought of this while coming in on a bumpy flight into Memphis, TN. The pilot of the airliner brought in the aircraft nicely, despite having to fight it quite a bit during the slowest portion of the approach. Now, Memphis is fairly flat, and the airport isn't near any large buildings so this isn't too much of a problem, but how do pilots practice bad weather approaches and takeoffs? It's kind of dicey to drop a newbie pilot into swirling bad weather, and I know as the aircraft gets smaller handling rough weather becomes harder. Is it done purely through simulators or do they use training flights where they intentionally fly during really rough weather? How does this training differ between general aviation and airline pilots?

I'd imagine flight simulators are good up to a point, but may not simulate all of the bad emergencies that could happen in bad weather (choppy crosswinds, hail, rain, lightning, etc.) so to train properly one would have to go up on training flights. However, I know that is very dangerous, and probably expensive, so it wouldn't be preferable. What platforms do current pilots use to get proficient at bad weather flying?

Your question has two components: 1) how do pilots train for adverse conditions and 2) how do pilots stay fresh on adverse conditions?

As you said, smaller airplanes (really, slower airplanes) are hardest, because the wind speed is a larger percentage of the airplane's flying speed. There are no real simulators for small airplanes: we learn by going out and doing. When you first learn to fly, your instructor makes sure you can handle crosswinds and gusts. With the Instrument Rating comes more adverse weather.

Once you have learned the techniques (and stay proficient by practicing regularly), faster airplanes and higher winds are not really a problem -- the same techniques apply, and in any case you will have a more experienced pilot or instructor helping you along.

I must call out your use of "newbie pilot" -- I hope you're not implying that airline pilots are newbies in any sense of the word. Before you can even hope to get an airline job you've already experienced bad weather in marginal airplanes.

Now, staying proficient: this is where transport airplanes (airlines) are very different from the small airplanes. The airlines' pilots practice regularly on simulators that really can duplicate just about any kind of weather you'd fly in. Pilots of small airplanes though... the simulators can't do that, and we practice in the real world.

All that said, a passenger's idea of what makes a good landing is very different from a pilot's! A passenger thinks a smooth touchdown is what makes a good landing. For a pilot, a good landing means a stable and controlled approach followed by an appropriate touchdown that maximizes safety -- in gusty crosswinds a firm touchdown is much safer than a greaser.


How do non-US pilots get the hours necessary for an ATP? I'm wondering about the possible lack of real-world flying experience by pilots in non-US carriers

In the US, aspiring airline pilots can work at a variety of jobs, like instructing, towing banners, crop dusting, etc, or part 135, to build time towards the 1250 hours now necessary for a restricted ATP to act as Second In Command (SIC) in carrier operations.

How do non-US pilots who don't have a military aviation background build the hours necessary to obtain an air carrier license in their own country? Are they all ex-military? Do they only need an ICAO-compliant commercial license and not an Air Transport Pilot License (ATPL)? Do we have 250- or 500-hour commercial pilots flying SIC into JFK?  Do these pilots have experience flying non-pushbutton aircraft?

Not sure if this is credible, but, as an example, there are fewer than 30 non-air carrier turboprops (Caravans, twin Cessnas, twin Beeches, and a lone Cheyenne) registered in Malaysia, and 10 are registered to the air force. The same site says Jordan has 7, 6 of them in the air force. Where are the national air carrier pilots getting their twin time? SIC in domestic carrier ATRs and Dash-8s?

Under the rules of ICAO Annex 1, Personnel Licensing, you don't need an ATP License to fly as second in command (SIC) on a commercial aircraft required to be operated with a co-pilot. A commercial pilot license (CPL) is sufficient to be SIC on an aircraft that requires to be operated by more than a single pilot.

And since 2006 ICAO have defined a Multi Crew Pilot License that also allows a pilot to be second in command on a commercial air transportation multi-crew aeroplane.

The  ICAO website about Multi-Crew Pilot Licence (MPL):

  The MPL allows a pilot to exercise the privileges of a co-pilot in a
  commercial air transportation on multi-crew aeroplanes. It provides
  the aviation community with an opportunity to train pilots directly
  for co-pilot duties. It is a new licence that has been introduced in
  addition to the existing pilot licences defined in Annex 1 — Personnel
  Licensing.

  The licence focuses on ab initio airline pilot training.
  MPL training and assessment will be competency-based and involve a
  multi-crew environment and threat and error management from the onset.
  It provides for greater use of flight simulation training devices and
  include mandatory upset training. At this stage, only aeroplanes are
  considered for this new licence. The details of the requirements for
  the licence are contained in Annex 1 — Personnel Licensing and in the
  Procedures for Air Navigation Services — Training (PANS-TRG). These
  documents outline the minimum international Standard for the
  implementation of the MPL by any State; they can be purchased directly
  from ICAO through the Document Sales Unit.

In Annex 1, the requirements are laid down for the MPL. One of the requirements says:

  Experience

  2.5.3.1 The applicant shall have completed in an approved training course not less than 240 hours as pilot flying and pilot
  not flying of actual and simulated flight.

The MPL, combined with a type rating, will get you to the right hand seat of the aircraft of choice.

So it's likely there are 250-to-500-hours commercial pilots flying Second In Command (SIC) into JFK. With experience in Beech Bonanza's, Cheyenne/Seminole, maybe CitationJet, a lot of simulator time and a couple of hours in a B777.

To answer your title question, in many countries pilots get their ATPL after building hours as SIC flying with a CPL or MPL within an airline training scheme.


Have there been instances where a LSA manufacturer has been audited? In theory, the authority to approve an LSA manufacturer and design has the right to audit their testing and work. What I'm interested in how often does this happen in practice, and whether there have been any cases of violations found because of this. Is the system of trusting manufacturers to be honest with their paperwork working so far?

Per this letter it appears that manufacturers who make LSA compliant aircraft are subject to a sort of enforced self regulation.  Basically, they are required to audit themselves every year and are told that the FAA could come and inspect their facility at any given moment, with heavy fines if an inspection is failed.

On top of this each aircraft itself is inspected by a technician before it leaves the facility to make sure that each aircraft meets the standards.

(The entire process is explained in more detail here.)

I did a bit of a search over a few of my favorite LSA news sites and I couldn't find any instances where an FAA inspection actually resulted in the proposed fines/punishments.  It seems that so far the semi-self-regulation model is working fairly well.  Well enough that, as Dan Johnson points out in that second article, it appears the FAA is considering using the same certification model for type aircraft as well.

To summarize, yes they are being audited, but by themselves.  It is also likely that outside bodies are auditing them as well, but nothing newsworthy seems to have come of any random inspections, so there is no mention of said audits.  I'm sure if somebody fails one, it will be big news.


Is anti-icing a small area of the windscreen (hot-plates) adequate for the full flight or only an interim solution? I asked this question about what "the thing on the windscreen of some Piper aircraft is". It came out that it is used as small anti-icing.

The user Jules asked following in a comment of an answer:

  Is de-icing this small an area generally beneficial for longer flights, or is it "just good enough" for a landing at the nearest airport if the ice buildup is starting to seem hazardous? (Asking as a non-pilot)

I also think it's a good question, but unfortunately the author of the answer didn't answer.

Thank you!

Those hot plates, in my experience, are useless.  The only reason we had one on our PA34 cargo plane was to make it legal for flight into known icing.  As far as I'm concerned, the whole and entire point of those external hot plates is to check a regulatory box to make the plane legal for FIKI if so certified.

It never once actually kept ice from accumulating and the entire windshield, hot plate included, frosted over on more than one occasion.  I recall hoping for strong right crosswinds so I could crab down to the runway using the side window.  We checked that the circuit was powered so we knew the plate had power, it was just totally ineffective.  Cutting a new pilot loose in that thing for their first low IFR icing encounter was a serious decision.

Now, proper heated windshields with integrated elements work wonders on ice.  They also cost $25k per side (twin Cessnas), so they'd better work.  The plates bonded to the windshields (on Barons, for example) seem to work OK too though I've never used one.  I think the cold air flowing over and under the stand-off hot plates simply overcomes the capabilities of the unit except in the most mild conditions.


How are coefficients of equation of sideslip angle in the paper "A general Solution to the Aircraft Trim Problem" calculated? I am sure many of you guys must have read the paper, "A General solution to the Aircraft Trim Problem" by Marco, Duke and Bernt. I am working with the turning of the Aircraft and I am not able to understand the calculation of Beta (sideslip angle) given in equation 72.

What I am able to understand is that the author describes the wind frame and body frame by 2 simple plane equations and then takes a dot product of the two planes to calculate beta.

The problem I am facing is with the calculation of the coefficients of the plane. They say that the coefficients can be expressed according to equation 67, which is nothing but axis transformation equations. Can anyone help me with the detailed calculation of those coefficients.

I have attached the above mentioned part as link to image file. Please have a look into it.

Link: A general solution to the Aircraft trim problem

First, some note on this paper: from my cursory reading, it always assumes zero atmsohperic wind relative to the ground. That's why the wind axis represents the true motion of the aircraft. In general, this is not true, therefore $\psi_W$ and $\theta_W$ are not the track and flight path angles.

Now onto your question. When you consider zero wind, then the angular difference between the y wind axis ($\hat{j}_{W}$) and the y body axis ($\hat{j}_{B}$) is the sideslip angle, $\beta$. This is consistent when you consider flow incidences as 3-2-1 Euler rotation from the body axis, where yaw (sideslip) is the last rotation:

$$C_{BW} = \begin{bmatrix}\cos\alpha\cos\beta & -\cos\alpha\sin\beta & -\sin\alpha \\
\sin\beta & \cos\beta & 0 \\
\sin\alpha\cos\beta & -\sin\alpha\sin\beta & \cos\alpha
\end{bmatrix}$$

Mathematically, this can be immediately seen when you rewrite the rotation matrix in its equivalent direction cosine form:

$$C_{BW} = \begin{bmatrix}\hat{i}_W \cdot \hat{i}_B & \hat{j}_W \cdot \hat{i}_B & \hat{k}_W \cdot \hat{i}_B \\
\hat{i}_W \cdot \hat{j}_B & \hat{j}_W \cdot \hat{j}_B & \hat{k}_W \cdot \hat{j}_B \\
\hat{i}_W \cdot \hat{k}_B & \hat{j}_W \cdot \hat{k}_B & \hat{k}_W \cdot \hat{k}_B\end{bmatrix}$$

So: $\cos{\beta}=\hat{j}_W \cdot \hat{j}_B$.

The gradient of the Cartesian equation of a plane is its unit normal, when normalized. For the $x_W z_W$ and $x_B z_B$ planes, the normal is simply their y axis (i.e. $\hat{j}_W$ and $\hat{j}_B$, respectively.

Lastly, eqn (72) can be worked out when $\begin{bmatrix}x & y & z\end{bmatrix}^T$ in the planar equations are in the inertial frame ($_V$), and transformed to the respective frames. The coefficients can then be derived and massaged to obtain (72).


Why does an Exhaust Gas Temperature (EGT) gauge require a power source? Why does the EGT gauge on jet engines require bus power if thermoelectric voltages generated by thermocouples are sufficient to move the needles?

The thermocouple voltage is a DC millivoltage. Presuming you’re talking about an analog gauge, there simply isn’t enough potential to “drive the pointer.” As such, that small voltage is usually amplified. The amplification requires that a larger power supply be used.

For a digital gauge, that millivoltage is capable of being read by a microprocessor, but the rhetorical question of “What powers the microprocessor?” Should be enough to resolve the rest of the question.


Why does the temperature rise in the boundary layer after a shock wave? Is it because the BL thickens after the shock so the drag increases, causing a increased friction? Here M=0.82 far from the airfoil, the picture represents the static temperature in Kelvins around the symetrical airfoil at angle of attack 0°.

This is the total temperature for a supposedly everywhere adiabatic flow.

This is not the static temperature but the Mach number, for $M_{\infty}=0.70$

Mach number for $M_{\infty}=0.80$

Mach number for $M_{\infty}=0.99$

Mach number for $M_{\infty}=1.20$

I understand that as velocity decreases, temperature rises, but I have another file that shows the evolution of static pressure and it does not increase as static temperature does, after the shock in the BL.

Thank you

Due to no-slip condition, the flow immediately adjacent to the wall has no velocity relative to the wall. If the flow is adiabatic everywhere and there is no significant viscous stresses (more on that later), then the total enthalpy ($h_0$) is constant; if we assume that the gas is calorically perfect (good assumption for air at low supersonic speeds) and that the heat capacity is constant (good assumption for small temperature variation), then:

$$h_0=c_pT_0=c_pT+\frac{1}{2}V^2$$

where $T$ is the static temperature, $T_0$ is the total temperature, $V$ is flow speed.

Immediately adjacent to the wall, the flow static temperature will increase toward the total temperature (around 315K in your example). This occurs in boundary layer both before the shock and after. The boundary layer before the shock is thin, so you can't really see it when zoomed out. After the shock, the boundary layer is greatly thickened along with an amplification in turbulence, so the effect is much more prominent.

Now let's revisit the part about viscous stresses, which are prevalent in the boundary layer. Viscous deceleration is not exactly adiabatic (Ref. Hill, Mechanics and Thermodynamics of Propulsion), so there is decreased total temperature immediately adjacent to the wall (characterized by the recovery factor), and an increase in total temperature farther away, before tending to the free-stream value.


What is a "core lock" on an jet-engine? This question came up while reading the Wikipedia article on core lock and Pinnacle Flight 3701.

If my understanding is right then if for example inner parts of the jet engine heats up that so much that the metal will expand, then after that it cools down rapidly it can result in a lock of the ball bearing of the blades. This means the engine is not functional anymore?

The Wikipedia article says that a windmill and a APU-restart is not possible anymore - is this because the engine has been rendered permanently inoperable?

Could somebody explain exactly what a core lock is to me, possibly with pictures?

There is a good writeup here that explains the engine issues as well as the rest of the incident you mentioned.

Core lock happens when parts inside the engine cool off at different rates, causing interference between them. In the case of the CF34 engines on these Bombardier jets:

  GE isolated the problem to contact between components of the high-pressure-turbine interstage seal - a static, pressurized honeycomb component - and the rotating seal teeth on the outer torque coupling.

Working on getting a good illustration of what they are talking about.

This does not mean that the engine is "not functional." There is just much more resistance on the rotating components, but once the temperatures have time to equalize, the components will break free.

  According to the NTSB, FDR data indicate that the engine cores were beginning to break free just before the impact.

During core lock, the resistance makes starting the engine more difficult. A windmill start does not provide very much turning force on the engine components, so the resistance from core lock makes that method of starting difficult. GE has done engine testing, and when the windmill restart fails, they are able to use bleed air from the other engine to restart the engine, which provides more turning force.


What is the relationship between drag and sink rate? I was just brushing up on basic aerodynamics and I have something I want to clarify about flying in the region of reverse command. I went up in my 172 the other day and noticed the following while practicing slow flight:

I'm on straight and level flight, and I enter slow flight (dirty) the way I usually do. I pull the power back and then I raise the nose to a level attitude slightly to bleed off some airspeed while maintaining the same altitude. When I entered the back side of the power curve, I pitched for an airspeed that was significantly above Vso, but below L/D max, which in this case happened to be 55-56 Knots. However, this time I didn't add any power and I just pitched for 55 knots to see what would happen. The airplane started descending (sinking), which is really what I expected it to do.

My limited understanding of why this happens is that total drag (mostly induced drag at high AOA) exceeds thrust available and the airplane develops a sink to try to regain equilibrium. Is this correct? Can someone with more knowledge explain why this happens? Maybe I'm overthinking it... I just know that high drag at low airspeeds typically results in a high sink rate. I just can't explain exactly why. Some people have said that weight exceeds lift, but I'm pretty sure this isn't the case as the airplane is not stalled.

total drag (mostly induced drag at high AOA) exceeds thrust available and the airplane develops a sink to try to regain equilibrium.

That is exactly right. At best L/D, induced drag is half of total drag and at lower speeds it becomes dominant, growing with the inverse of airspeed squared.

  Some people have said that weight exceeds lift, but I'm pretty sure this isn't the case.

You did well not to listen to those people. If the aircraft doesn't accelerate downwards, lift still equals weight. At a constant sink rate the aircraft does not accelerate.

As you say, the aircraft is in an equilibrium. Because you choose to add less power than what was necessary for level flight, the aircraft behaved similar to a glider. Allow me to use a glider for my explanation. Below is one with the dominant forces added as arrows in level flight. Clearly, there is nothing to compensate drag (red):

This airplane is not in equilibrium and does what you did in order to slow down: It flies level while drag is exceeding thrust (which is per definition zero in a glider).

So what to do? Just like when flying a turn, the pilot will now tilt the lift vector. That is the biggest force at his command, and he does so by pitching down. Now the airplane is in a glide, the direction of flight is slightly down and the lift vector (which is per definition perpendicular to the direction of the airspeed, which again is equal to the direction of flight if there is no wind) is equally tilted forward. This is what the next sketch shows:

Now we have a component of lift pointing forward, and that component is equal and opposite to drag. The rest of the lift is needed to compensate the weight, so the lift force is a tiny amount larger than weight. The sink rate is speed times the tilt angle, which in turn is what is needed to have the sine of lift $L$ equal drag $D$. Mathematically speaking, this is:
$$D = L\cdot sin(\gamma)\;\;\;\text{and}\;\;\;\gamma = arcsin\left(\frac{D}{L}\right)$$
with $\gamma$ as the angle of the direction of flight relative to the horizon.
The sink rate $v_z$ is $$v_z = v\cdot sin(\gamma) = v\cdot\frac{D}{L}$$
That is the direct answer to your question: The sink rate is the product of speed and the inverse of the lift-to-drag ratio. At small angles the ratio is approximately equal to its sine when expressed in radians, so I left the trigonometry out of the last equation.


How do balloon pilots avoid birdstrikes? Balloons, by their very nature, are at the mercy of the wind, and can’t maneuver out of the way of other objects except by (very slowly) climbing or descending.  For this reason, mid-air collisions are fairly common whenever and wherever large numbers of balloons occupy small volumes of airspace (especially because this inability to take evasive action essentially restricts most balloons to uncontrolled airspace, which, in most places, is a very small layer immediately above the ground); fortunately, as balloons are very slow1 and very soft, balloon-balloon MACs are, generally, completely harmless (except in the extremely rare cases where a balloon rises into the basket of a balloon above it and gets its envelope ripped open).

Birds, on the other hand, are not necessarily at the mercy of the wind, are largely concentrated at the low altitudes where most balloons operate, are far more numerous than balloons (which is probably still the case even in the middle of a balloon gathering), and tend to come with a lot of inconsiderate pointy bits (beak, claws, probably other things too).  Unlike with heavier-than-air aircraft, where a birdstrike usually just means a few dents, or, at worst, some unscheduled engine maintenance (although, as always, there are exceptions), a balloon could, if hit by a bird, easily suffer a catastrophic envelope rupture, followed quickly by (at best) a hard forced landing, or (at worst) rapid unscheduled lithobraking.2

How do balloons and birds avoid each other?

1: Not necessarily slow relative to the ground, but definitely slow relative to each other (since they’re being pushed by the same, or mostly the same, wind), which is what counts in a MAC.

2: Like the chapter in The Twenty-One Balloons where the protagonist’s houseballoon is punctured by a seagull, and he has to make a forced landing on a beach.

The airspeed of a hot air balloon is always... zero.  So it's completely up to the bird to do the avoiding.  Which shouldn't be too difficult for the bird, on account of this humongous giant brightly coloured monster thing floating in its way.  Ya gotta be a pretty dumb or drunk bird to run into one.


Why are so many small private jets sold just after a few years? Why are so many small private jets sold within few years? Hardly a year or two, with depreciation of over 1-2 million dollars?

I understand these are bought by millionaires. But everyone spends some time while making such a huge investment. I presume they decided to own the aircraft and might have tried it for a few hours before procuring one. Hence, being stupid, repenting and selling it off for the majority of the buyers.

If millions are peanuts for an owner, he would be into the bigger jets like Learjet or Gulfstream.

So, why are smaller jets with < 12 pax sold in the used market so fast? Of which many hardly have ~200 hours on them. This doesn't make any economic sense to a small millionaire.

Are there any additional benefits (e.g., tax benefits) by spinning off an airplane the next year after procuring it?

In the United States, aircraft that are owned and operated by businesses are often depreciable for income tax purposes under something called the Modified Accelerated Cost Recovery System (MACRS).

  This is beneficial since faster acceleration allows individuals and
  businesses to deduct greater amounts during the first few years of an
  asset's life, and relatively less later. (Emphasis mine)

But even more so, The 2017 Tax Cuts and Jobs Act provides for 100 percent bonus depreciation, allowing taxpayers immediate deduction of the cost of aircraft acquired and placed in service after Sept. 27, 2017 and before Jan. 1, 2027.

This means that perhaps if someone were to have a financial windfall (sale of a company, or a large sale of highly appreciated stock), they could purchase a rather expensive airplane, and if used for business purposes (generally at least 50%), they could offset their taxes for the entire purchase price of the aircraft in the first year!

To have an overly simplistic example: Say you had $10 million in ordinary taxable income this year. You could reduce that by purchasing a, oh let's say a (2020 List price approx) 2.6 million Cirrus Vision SF50 Jet. You'd be able to reduce your taxable income by 2.6 million and pay taxes on "just" 7.4 million.  Now say at least one year later, you could sell your jet and pay depreciation recapture long-term capital gains tax (which depends on the amount of your ordinary income and is capped at 25% ... which is less than the 2020 37% top tax bracket).  This would have saved you in this example 312,000 (12% of 2.6 million) in a year. Of course, I'm sure it's a little more complicated than this oversimplified example, but you can see how it might be advantageous from a tax perspective, if you have a large income where you can benefit from the 100% depreciation in the first year.

So yes, it could be a tax play. Or it could be like so many things, what you thought was fast/big before you got it, now you have it, and you start to notice faster, bigger things and want to upgrade :)


How to perform climbs and descents? I have known that when you climb, you push the throttle to maximum and adjust the vertical speed with the commands (elevator) and the trim. Then when you reach the desired altitude you pull the throttle to cruise RPM setting (2350 for example) and it will maintain level.

For descents you pull the throttle to decrease RPM and you adjust your vertical speed with the commands and the trim again. Then when you reach the desired altitude you push the throttle to cruise RPM setting again and it will maintain level.

Obviously, using the carb heat (hot when lowering down the RPM and cold when increasing).

Is this correct? Is there a better way to perform this maneuvers?
Thanks, and sorry for the noob question.

To enter the climb, it's power, attitude, trim. That is, start by setting climb power, as you already know. Remember to compensate for adverse yaw with the rudder. Immediately raise the nose to the climb attitude. Your instructor will teach you to recognise what this looks like in your aircraft: e.g. there might be a part of the dash that lines up with the horizon. Your airspeed will drop away to the desired airspeed for the climb: usually the best-climb speed. Once you're stable and balanced, at the correct airspeed, use the elevator trim to remove the need for pressure on the stick (or yoke).

To level off from the climb, it's attitude, power, trim. Start by lowering the nose to a level attitude. You need to start doing this before you reach the desired height, as it takes a few seconds to level off. Once you're level, the airplane will speed up. When you reach cruise speed, reduce the power to cruise power, and compensate for adverse yaw. Again, once you're stable at the correct speed, trim away any constant pressure on the stick.

A gliding or powered descent is similar. Power, attitude, trim to enter the descent. First set the reduced or idle power, and wait for your airspeed to decay to the correct airspeed for your descent. When you reach this airspeed, lower the nose to the glide attitude. Once the attitude and speed are stable, trim the aircraft.

To level off from the descent, it's power, attitude, trim again. Anticipate reaching the height you want, just like when climbing. Raise the throttle to cruise power. Adding power will naturally cause a pitch-up tendency in most airplanes, so let the nose come up to the level attitude, and then you'll need forward pressure on the stick to keep it there. Once you're stable and level, trim away that forward pressure.

So for most of these attitude changes, the sequence of events is power, attitude, trim (PAT as a mnemonic). Leaving a climb is different: there it's APT, because lowering the nose first lets the speed increase to the cruising speed before you need to touch the throttle. Whenever you change power, you'll need to use rudder to compensate for adverse yaw.

Generally, you maintain the correct rate of climb or descent by keeping the correct airspeed, not by looking at the vertical speed indicator. Usually you just want the best rate of climb or descent, and you'll already know what airspeed achieves this, so it's easy to just check the airspeed indicator every so often and pitch up if you're too fast, or down if you're too slow. There are circumstances where you need to keep a particular rate of climb or descent, but that's not the norm so it's not what's taught first to student pilots.

The Pilots' Operating Handbook for the aircraft you're flying will tell you when carb heat is needed. In general, you should have it hot when you're at idle or low power (i.e. in the descent), and cold the rest of the time.


Is the CV-22 / MV-22 Osprey classified as a Helicopter, Plane or Both? Is the CV-22 / MV-22 Osprey classified as a Helicopter, Plane or Both?
If the President had to hitch a ride on one, would it become Airforce One(CV-22) and Marine One(MV-22)?

They are classified as Tiltrotors, which is its own category for all the obvious reasons.
If the President were flying in a Marine Osprey, the callsign would be Marine One. If he were in an Air Force Osprey, it'd be Air Force One.


Why was the tip of the B-52's vertical tail chopped off in 1959? When Boeing switched over from the B-52F to the B-52G in 1959, they (among other changes) lopped off the top 2.4 meters (8 feet) of the aircraft's vertical tail:
Original-height tail (here on a B-52F)

(Image by the United States Air Force, via David Legrand at Wikimedia Commons, edited by Denniss, Hohum, and Ralf Roletschek at Wikimedia Commons.)
Pruned tail (here on a B-52H)

(Image by the United States Air Force, via Trevor MacInnis at WIkipedia, via Rcbutcher at Wikimedia Commons.)
Why did they chop off the tip of the vertical tail, thereby decreasing the aircraft's directional stability and rudder authority?

Boeing B-52G Stratofortress

  In the design of the B-52G, considerable attention was paid to reducing the structural weight. Different materials were used in the construction of the airframe, and the wing structure was extensively redesigned. The most visible difference was a vertical tail which was reduced in size. The height was reduced from 48 feet 3 inches to 40 feet 7 inches, and the chord (width) was increased. The new tail was tested on the first B-52A (52-001) and perhaps also on either the XB-52 or YB-52 before being adopted as standard for the B-52G.


Do commercial aeroplanes use ABS to brake? I have read that the wheel brakes on an aeroplane are by for the most efficient means of stopping it. I was wondering whether in low grip situations, such as in rain or snow, an ABS (Anti-lock Braking System) system is used to ensure the wheels do not lock. If not, why is this not necessary?

Yes, they do. They are called Anti-Skid and they go from Mark I of 1948, with simply an on-off switch triggered by wheel lock, till Mark V (or at least that's the last I've seen), with quite complex control systems and sensors behind.

The full details are a bit long to include them all here (there are entire book sections about them). For a brief overview, see this presentation from slide 12 till 18.


What area to use for the lift/drag forces I'm trying to model the orbit of a satellite around the earth at 500km above the surface. I have the nose cone radius and the surface area of the wings so should I be using the cone radius for the drag and the wing area for the lift or wing area for both of them?

If you're using equations with $C_L$ and $C_D$ you need a (single) reference area, $S_{ref}$:

$$L = q_\infty S_{ref} C_L$$
$$D = q_\infty S_{ref} C_D$$

For aircraft this is generally the wing planform area. However, for a satellite, wings aren't going to be of much use, so the area upon which molecules will be impinging (such as the nose cone or cross sectional area normal to the flow) would be a more useful choice. Your coefficients will vary depending on which area you choose. Note that it really doesn't make sense to try to model the "lift" of a satellite.

On that note, satellites, especially at altitudes as high as 500 km, are essentially ballistic, so the ballistic coefficient is perhaps a better choice:

$$ BC = \frac{M}{C_d A} $$

Here $A$ is the cross sectional area of your object, but for all intents and purposes it's very similar to $S_{ref}$. We can substitute it back into the drag equation to get something useful for satellites:

$$ D = \frac{q_\infty M}{BC} $$


How high does the "bug layer" extend? As far as I know, a big obstacle to attaining laminar flow in aircraft today is the so-called "bug layer", presumably a lower layer of the atmosphere where bugs are encountered. So, my question is simply this: how high up do insects stop becoming a serious issue for laminar flow?

In 1961 study a plane flew 116,684 miles sampling the air, catching whatever was up there, and managed to capture a single termite at 19,000 feet. This is the highest ever observed.

You just never get above the "bug layer" in a smaller aircraft (Cessna 172 limit is 15,000 feet). Likely this is not a proper naming.


How are the compressor and turbine disks connected? What is the typical way the compressor and turbine disks connected to (LP/HP) shaft ? How are the disks connected to each other  (e.g., curvic coupling, bolts or others ?)

From The Jet Engine, Rolls Royce, issue 5: a compressor drum assembly. There are holes at the lower bit which attaches to the shaft, and another section of the book mentions hundreds of holes for bolts. These holes might be for fasteners.


AIP, AIC, NOTAM, ANO (UK): How do they relate to Annex 15 of Chicago Convention? I've recently started studying for my Air Law and Meteorology exam and am trying to get my head around some of the basic literature / legal documentation structure.

As I understand it the Chicago Convention outlined a series of ICAO Articles that are available in detail as Annexes. These are introduced into law in the UK via the Air Navigation Order.
I'm having some confusion understanding the AIP and how this relates back to the ANO, if at all. Not only this but also what the main differences between an AIP, AIC and NOTAM are.

Is anyone able to help by concisely explaining how these entities relate to one another and how they differ so that I can build a mental image before studying each further, I would greatly appreciate it.

Annex 15 of ICAO Chicago convention describes the required information for safe conduct of flights, and which aeronautical information is to be provided by ICAO members. Each country needs to provide an aeronautical information service (AIS) in a standardized form, comprising static and dynamic data.

Static: Aeronautical information publication (AIP), AIP amendments and charts. AIP is generally updated each 28 days.
Dynamic: Notam, AIP supplements.

Explanatory information doesn't fit well in the previous categories, and is grouped in aeronautical information circulars (AIC).

Details

AIP: Authoritative information issued by an ICAO member containing long lasting aeronautical information essential to air navigation.AIP list by country.
AIP amendment:  Permanent change to AIP.
AIP supplement: Temporary change to AIP.
Notam (and Snowtam): Notice distributed by a telecommunication system, concerning the establishment, condition or change in any aeronautical facility, service, procedure or hazard, the timely knowledge of which is essential to personnel concerned with flight operations. Also associated with Notam: pre-flight information bulletin (PIB), a presentation of current Notam information of operational significance, prepared prior to flight.Notams in US.
AIC: Information that doesn't qualify for inclusion in AIP or Notams but which relates to flight safety, air navigation, technical, administrative or legislative matters. This could include mid-term prevision for changes in the regulatory or technical frameworks, results of safety investigations, scientific discovery related to how weather impacts aviation...List of Canada AIC.

Full aeronautical information contains:

AIP, including amendments
Supplements to the AIP
Notams
AIC
Checklists and lists of valid Notams.

Source for the above definitions: Manual of Aeronautical Information Services, India.

Regarding The Air Navigation Order (ANO), specific to UK

  "On 7 December 1944, the majority of the world's nations became
  signatories to the "Chicago Convention", the aim of which was to
  assure the safe, orderly and economic development of air transport.
  ICAO sets out, in the terms of the convention, the rules, regulations
  and requirements to which each signatory must adhere. The Civil
  Aviation Act 1982 is the UK's means of discharging its ICAO
  responsibilities. This legislation required the creation of the CAA.
  The Air Navigation Order (ANO) is the law that empowers us to carry
  out our duties."

Source.

ANO is the legal framework valid for UK, to empower aeronautical agencies and their publications, in accordance with Annex 15.


B777- In emergency mechanical back up how does the flight controls manage engine failure In case of engine failure above the ocean with multiple electrical failures and after having exhausted the batteries the fly by wire mechanical backup with available hydraulics if left with the THS and one spoiler per wing under the control of the control wheel, How in these conditions the pilot will manage the asymmetrical thrust?

Basically thrust asymmetry is normally managed with the rudder, the schematic shows in mechanical backup the rudder is not Available, while the remaining spoilers 4 and 11 are rather for roll control, what can do the pilot?

N.B. June 17, 2019: if it is difficult to imagine one engine failure + total electrical failure, please imagine an engine failure + Total FBW computers and controllers failure, the most important is to go into the mechanical mode as described here below with an engine failure:

In your scenario there would likely still be hydraulic power and electrical power from the one running engine and the RAT (Ram Air Turbine) generator, which can power everything except the autopilot. The TAC (Thrust Asymmetry Compensation) system would compensate for the asymmetric thrust.


Does the direction of counter-rotating props affect efficiency? From my brief Wikipedying, if counter-rotating props' tops go towards each other, each has a reduced P-factor so the loss of either engine won't yaw the aircraft as hard as if the bottoms come together.

As I don't really care about safety of my aircraft's occupants (usually a couple ants after it sits on the grass) or reliability, I'd prefer to increase the P-factor for fun and flat spin potential. Out of curiosity, does the direction of counter-rotating props (rather, counter- or similar- in a twin) affect the efficiency?

It might. Depending on how close to the wingtips your props are.

If you put the props right at the wingtips, then the conventional rotation to minimize precession and torque actually decreases efficiency by promoting tip vortex (the direction of the prop is the same as tip vortex thereby adding to tip vortex). This reduces lift for the same amount of airspeed.

On the other hand, rotating it the other way round - away from each other - reduces tip vortex by twisting the slipstream the opposite direction as the tip vortex. This increases lift (technically, it reduces the reduction of lift due to tip vortex) for the same amount of airspeed.

One plane that exploited this was the Vought XF5U - the Flying Pancake. The direction of prop rotation is fairly obvious in this picture:

The interesting result of this was that even though the XF5U had very short wingspan it could do short take-offs.


Is it possible to isolate COM1 and COM2 on a Garmin G1000? Is it possible to isolate COM1 to one pilot and COM2 to the other pilot?

When I'm getting the ATIS it's hard to listen to both COM channels sometimes depending on the amount of traffic.

I used to be able to do this on an older aircraft I flew, and loved the feature in a crew environment.

(wikimedia.org)

On the audio panel installed between the two G1000s, there should be a COM 1/2 key. That will enable the split COM operation with COM1 going to the pilot and COM2 going to the copilot.  What avionics are in the aircraft that you have?

  Split COM allows the pilot to use COM1 while the copilot uses COM2. This proves very helpful for talking to an FSS en route without leaving the ARTCC frequency. Pressing the COM 1/2 key on the audio panel turns on Split COM mode (Garmin).


How do seaplanes do run-up checks without brakes? Usually on run-up you want to check the response of the motor when changing for example the carb-heat (if existent). At least we did so on my intro flight (yey!). To prevent us from rolling onto the active runway we (obviously) held the brakes.

Now I wondered how pilots of floating planes and flying boats prevent movement on pre-takeoff checks. Additionally most images I found from flying boats they usually have more than one engine. Similar question here: How do pilots prevent swimming circles as one engine is started and the other(s) is/are not?

I scanned this FAA document from this related question but that is mostly is about landing (which is interesting as well but I assume that as in the linked question the airframe and especially the water resistance take care of that).

I'll limit my answer to single-engine seaplanes as I've never flown a multi-engine seaplane.

Typically there is no need to stay stationary in the water when doing a run-up. Just do it while taxiing to your takeoff path, or you can do it on your takeoff path. If the takeoff path isn't long enough to do the run-up and then continue along the path for the takeoff, you can turn around, taxi back along the takeoff path, and then takeoff.

At typical run-up power settings, if you hold full up elevator, the airplane will simply mush along on the water since you won't have anywhere near enough power to get it up on the step. In other words, you won't be going very fast.

When giving floatplane instruction, one of the first things I tried to impress on students was to not think in terms of the constraints of straight, hard-surface, defined runways, taxiways and the like. There's no need, typically, to taxi in a straight line, make well-defined taxiing turns, and no need to takeoff in a straight line. Once away from the dock or beach, the airplane is going to weather vane unless you actively oppose that, and that weathervaning is going to have a component caused by the current, if any, of the water you're on.

In my experience, most of the time the takeoff path was either dictated directionally (a river) or pretty much wide open (lake or reservoir). For new students in my area, reservoirs were preferred. More often than not, it was a matter of getting a short ways off the dock, do the checks other than the run-up while moving away from the shore at a 90 degree angle more or less, lift the water rudder, bring the stick all the way back, and do the run-up, all the while letting the aircraft weathervane into the wind. Then just takeoff.

I never flew a twin-engined seaplane, but I see no reason why you couldn't bring both engines up to the run-up rpm, do the checks on one and then the other. While checking the mags, carb heat, and props, there would be a little asymmetrical thrust, but not enough that the rudder couldn't handle that.


What things do you consider when choosing a fixed base operator (FBO)? I'm working on some marketing for a regional FBO and while I'm an aviation aficionado, I'm neither a pilot or deeply involved in the aviation industry.

I'd love your input on how you research and choose an FBO while doing your flight planning…

As a pilot what are your primary considerations when choosing an FBO? Fuel cost, amenities, local knowledge, other things entirely?
What things do you look at as distinguishing factors between competitors?
Are there certain things that you consider mandatory from an FBO?
What information do you want to "know before you go"?
What online resources do you personally use when doing your flight planning and/or researching FBO's?
Have you had an extremely positive (or terrible) experience with an FBO, so that I can research them?

I'll also note that this particular FBO is located in a fairly rural, yet growing region of the Western United States.

Look forward to your input and responses!

I'll throw in my 2 cents here but I am by no means super experienced in this realm.

Amenities is not a huge deal for me. Generally I fly to go somewhere, while a nice interior is always a bonus, I'm fine as long as there is a bathroom and a receptionist to pay. Generally I'm at the airport to tie up and then leave and go about my business. Some place to sit to wait for weather to improve is nice but I by no means care if the couch is leather or 1970's velour as long as I can sit on it for a while.
I flight plan with ForeFlight.com so I won't comment on what you should have but in today's day and age I would consider a WiFi connection in the FBO a must have since lots of people use tablet based planning now.
Fuel cost is always a consideration and you should try and remain competitive to your local areas as much as possible.
The key for me is a well laid out and clear website that lists prices for what ever you offer and other important information. Maybe an airport map with the location of the FBO clearly marked. A phone number to call for questions is also important.
A solid relationship with a local taxi service is a bonus and a courtesy or rental car would be even better, but I understand how this could be a runaway cost on some level.
Local knowledge is good if there are specific things that may be odd about the airspace and major airport issues that may arise.


Does the nose-up attitude of a jet make it more difficult to land than a turboprop? Due to the more acute nose down attitude of a turboprop on approach, does this make it less difficult to control compared to the relatively high nose up attitude of a jet?

You're asking, I think, two questions. The first in the title is very general; the second in the text relates to control as affected by aircraft pitch on the approach. The answers to both are going to be somewhat opinion based as well as depending on which turboprops and which jets you're talking about.

My thoughts are based on the following turboprops: King Air A90, Swearingen SA-226 and 227, Fokker F-27; and on the following jets: Cessna Citation 500, Boeing 727-100, and Boeing 747-100/200.

In my opinion, there is no general practical difference in the difficulty or ease of approaches and landings based on whether you're in a turboprop or a jet or what your pitch angle on the approach is. Some might say that a nose down attitude is going to give you better visibility. However, I never found that lack of visibility over the nose was a problem.

There are differences in the characteristics of turboprops and jets that make the one or the other the better approach and landing vehicle in certain circumstances. For example, if you need a quick descent, you can flatten out the pitch of a turboprop and get a lot of drag, more if you move into beta. For jets, the engines are always going to be producing some forward thrust (although I seem to remember the DC-8 allowed idle reverse in flight).

If you have a crosswind, the heavier the aircraft and the higher the landing speed, the easier it will be to handle the cross wind, and transport category jets in general are heavier than turboprops. Also, in a crosswind, a high wing is considered a liability, and there are a lot of high wing turboprops.

I guess what I'm saying is that individual aircraft and circumstances outweigh differences between turboprops and jets insofar as approach and landing is concerned.

The hardest and easiest aircraft I flew insofar as getting a good touchdown were both jets: the hardest being the 727-100 and easiest the 747.

The most flexible insofar as the approach was concerned were the SA-226/227. You could fly the approach clean at near-jet speeds and then slow down very quickly on short final. KSFO controllers back in the 1980s used to appreciate our ability to fit in. Or they could bring us in on a close-in downwind and then have us dump it for a well-timed turn to base and then a very short final.

---------- Edit for additional information

@JanHudec pointed out that turboprops have a faster response to power changes than jets. That's true, though in day to day flying, you plan for what you have. Obviously, though, in an emergency situation that required additional power, the turboprop would enjoy the advantage.

The difference in response to adding power is not as great as it used to be. As I remember, when the 727 first came out, there were a couple of incidences of 727s touching down slightly short of the runway because of the time required for the engines to spool up. The figure that sticks in my mind is that for those first engines, the time from full idle to full power was 7 seconds. Boeing fixed the problem by putting in a flight idle and a ground idle. The flight idle kept the engines spooled significantly higher than the ground idle. That involved no change to where you placed the thrust levers. You brought them all the way back. If you were still in the air, that wouldn't spool the engines all the way to full idle.

The 747 engines reacted very quickly, much more so than the 727 even with the flight idle setting. I remember two instances in the 747 in heavy gusting crosswinds where I used a lot of power at the last moment. In the 727 those touchdowns might have been a lot harder? In a turboprop maybe a little less hard?


Are helicopter pilots required to use GPS navigation? Some helicopter crashes are caused by a disoriented pilot. This would presumably be impossible with a GPS with terrain maps. Are pilots required to use a GPS when flying a helicopter in the US?

No, pilots are not required to use GPS maps or moving GPS while flying helicopters or fixed-wing aircraft.

There are some approaches to landing that require GPS (called RNAV) approaches, but the airports that they serve usually have other types of non-precision approaches as well.

Helicopters have specialized maps that are called Helicopter Route Charts that are supposed to provide additional information relevant to helicopter pilots. These charts may be carried in paper form, although newer aircraft also have them as electronic moving maps. The pilots may also (but are not required to) be using electronic flight bags with moving maps/terrain/synthetic vision.


At what position or distance from an airport are you considered to be in the "traffic pattern" image source

In the United States, as an aircraft is approaching or departing a
non-towered airport, at what position or distance from the airport
are you considered to be in or out of the "traffic pattern".
Is it different for an airport with a operating tower?
Does it vary with other countries?

Hint: a regulation exists but it is not in part 61 or 91 (think, space shuttle)...

This AC describes a fair bit of what/where a traffic pattern is. ultimately it comes down to definition but the answer seems to be what ever the defined traffic pattern says

  The airport traffic patterns described in part 93 relate primarily to
  those airports where there is a need for unique traffic pattern
  procedures not provided for in part 91. Part 97 addresses instrument
  approach procedures (IAP). At airports without operating control
  towers, part 91 requires only that pilots of airplanes approaching to
  land make all turns to the left, unless light signals or visual
  markings indicate that turns should be made to the right

It seems they are somewhat careful to not explicitly define anything and instead allow some definitions to define it for explicit cases and others to be left to interpretations. The FAA advises that calls be made as far as 10 miles out.

The FAA technically allows airports to define their traffic pattern themselves:

  Traffic Pattern Design. Airport owners and operators, in coordination
  with the FAA, are responsible for establishing traffic patterns. The
  FAA encourages airport owners and operators to establish traffic
  patterns as recommended in this AC. Further, left traffic patterns
  should be established, except where obstacles, terrain, and
  noise-sensitive areas dictate otherwise

They do provide some guidance on how to do so in regards to altitude they even allow the pilot to decide

  Traffic Pattern Altitudes. It is recommended that airplanes observe a
  1,000 foot above ground level (AGL) traffic pattern altitude. Large
  and turbine-powered airplanes should enter the traffic pattern at an
  altitude of 1,500 feet AGL or 500 feet above the established pattern
  altitude. Ultralight aircraft should operate no higher than 500 feet
  below the powered aircraft pattern altitude. A pilot may vary the size
  of the traffic pattern depending on the aircraft’s performance
  characteristics

Going straight to regulations taken from here

  §91.127   Operating on or in the vicinity of an airport in Class E airspace.

  (b) Departures. Each pilot of an aircraft must comply with
  any traffic patterns established for that airport in part 93 of this
  chapter.

and for class D

  §91.129   Operations in Class D airspace.

  (1) Unless required by the applicable distance-from-cloud criteria, each pilot operating a
  large or turbine-powered airplane must enter the traffic pattern at an
  altitude of at least 1,500 feet above the elevation of the airport and
  maintain at least 1,500 feet until further descent is required for a
  safe landing.

and Class C

  §91.130   Operations in Class C airspace.

  (b) Traffic patterns. No person may take off or land an aircraft at a satellite airport within
  a Class C airspace area except in compliance with FAA arrival and
  departure traffic patterns.

If the tower is in operation they can vector you as they see fit (at least here under the FAA) as such they may use pattern terms and organization but I cant tell if the FAA considers it a pattern or not if there is a tower.


What is the requirement to become a flight attendant? We know that flight attendants, on top of serving passengers (which is what they do 99% of the time), are there to ensure the safety of passengers on board. For example, they are trained to operate emergency equipment in the event it is necessary.

What is the legal requirement to become a flight attendant? I am not asking how one can get hired (which may involve speaking different languages, being friendly to customers etc.), but how one can serve as a flight attendant on a commercial flight recognized by aviation authority.

There is a (relatively) new requirement for Flight Attendants (on aircraft with more than 20 passenger seats) to be certified as per the FAA. This was done in the "VISION 100—CENTURY OF AVIATION
REAUTHORIZATION ACT", in section 814 if you want to read it.

The applicable CFR is 49 U.S. Code § 44728 - Flight attendant certification. In summary it says:

You have to have a certificate of demonstrated proficiency, this looks like a pilots license.
Demonstrated compliance with the air carrier approved training program.
Proficiency to read, speak, and write English
Comprehend written material in English
Ability to write incident reports and log entries/statements
Carry out written and oral instructions

Now, the actual physical requirements are up to the airline, as long as the individual can complete the training program, they are physically allowed to become a flight attendant (physical appearance requirements aside). As for "legally" allowed, they need to be able to pass the same TSA background checks that pilots are subject to. So legally, almost all airlines require:

U.S. Citizen or appropriate work visa
Be able to enter/exit the United States without any issues (no visa problems with other countries, although for regionals this may not apply)
Be able to pass a TSA/FBI background check
No DUI or felony convictions within the past 10 years

There isn't a lot more "legal" to it than that, they don't have to demonstrate the use of safety equipment if the airline's training program doesn't require it.


Drag coefficient and lift coefficient What happens if drag coefficient increases but the lift coefficient remain the same?

In that case, you'll need to increase the power in order to keep your airspeed and stay airborne. The extra power will be spent in fighting the extra drag... Besides, you'll have to reduce AoA in order to keep total lift equal to the weight and thus stay at the same altitude...


What is the major source of engine noise for non-propeller aircraft? Sparked by this question:

Take any non-propeller powered aircraft, when idle, the sound produced by the engines are fairly low pitched, and as the engine spins up, increasing in pitch before becoming a full on roar.

I figured that the major sources of engine noise could be

The air rushing out of the exhaust,
The noise of combustion in the engine,
The mechanical noise of engine parts

My question is what causes the majority of the engine noise at idle vs full power.

To stop this question being too broad, lets discount noise coming from any source that's not the engine's of the aircraft in question. I just want to know about engine noise.

I had a look at this question, but that doesn't have any information about the source of engine noise, just that the turbine itself will also produce noise which is something I didn't consider.

At full power it is the mixing process of the fast exhaust flow with the surrounding air. Note that noise increases with the sixth to eighth power of jet velocity, so the loudest engines are those with a low bypass ratio  and reheat on.

Diagram from a Stanford web page on noise. The jet velocity is in ft/s.

At idle the biggest noise source of the whole aircraft is the flow around the lowered landing gear, gear cavities and the slotted flaps that you asked us to disregard. The engine noise is a combination of intake noise, bearing noise and nozzle noise, and which of those contributes most to the engine noise depends on the individual engine and its installation into the aircraft.


Which was the first pressurized aircraft? Which aircraft was the first one to fly pressurized?

High altitude breathing apparatus, 1918 (source)

I mean an aircraft which didn't require to don an oxygen mask above a certain altitude, excluding very high altitude where a mask is still required due to quick loss of consciousness after a depressurization event.

The history section of the cabin pressurization Wikipedia article names a few based on the feat:

  The aircraft that pioneered pressurized cabin systems include:

  Packard-Le Père LUSAC-11, (1920, a modified French design, not actually pressurized but with an enclosed, oxygen enriched cockpit)
  Engineering Division USD-9A, a modified Airco DH.9A (1921 - the first aircraft to fly with the addition of a pressurized cockpit module)
  Junkers Ju 49 (1931 - a German experimental aircraft purpose-built to test the concept of cabin pressurization)
  Farman F.1000 (1932 - a French record breaking pressurized cockpit, experimental aircraft)
  Chizhevski BOK-1 (1936 - a Russian experimental aircraft)
  Lockheed XC-35 (1937 - an American pressurized aircraft. Rather than a pressure capsule enclosing the cockpit, the monocoque fuselage skin was the pressure vessel.)
  Renard R.35 (1938 - the first pressurized piston airliner, which crashed on first flight)
  Boeing 307 (1938 - the first pressurized airliner to enter commercial service)
  Lockheed Constellation (1943 - the first pressurized airliner in wide service)
  Avro Tudor (1946 - first British pressurized airliner)
  de Havilland Comet (British, Comet 1 1949 - the first jetliner, Comet 4 1958 - resolving the Comet 1 problems)
  Tupolev Tu-144 and Concorde (1968 USSR and 1969 Anglo-French respectively - first to operate at very high altitude)
  SyberJet SJ30 (2005) First civilian business jet to certify 12.0 psi pressurization system allowing for a sea level cabin at 41,000 ft (12,000 m).

If it is the whole plane and not just the cockpit, then we're looking at the Lockheed XC-35, or the Junkers Ju 49 (whose purpose was to investigate the techniques of cabin pressurization).

For the first in service, then it's the Boeing 307 Stratoliner.

XC-35 (top) and the modified enclosed cockpit of the USD-9A.


Why do the inlet cones on an SR-71 retract at higher speeds while the one on a MiG-21 extends at higher speeds? As shown by this illustration in the SR-71 flight manual, its inlet cones (spikes) retract as its speed increases:

 (source)

Meanwhile, the Wikipedia page for the MiG-21 describes the opposite behavior for its intake cone:

  On early model MiG-21s, the cone has three positions. For speeds up to Mach 1.5 the cone is fully retracted to the maximum aft position. For speeds between Mach 1.5 and Mach 1.9 the cone moves to the middle position. For speeds higher than Mach 1.9 the cone moves to the maximum forward position.

No source is provided for this part of the Wikipedia article. If the info about the MiG-21 is accurate, why does its intake cone behave differently than the SR-71's? Do the two aircraft's intake cones serve different aerodynamic purposes?

This is only a guess, so please take this with a grain of salt.

An important characteristic of supersonic engine inlets is the total pressure loss (or also sometimes pressure recovery). The total pressure loss over a normal shockwave is a lot higher than if you would slow down the air to the same speed through several oblique shock waves.

If you want to understand why the sr-71 spike retracts I recommend you watch this video. The sr-71 had a quite complex inlet geometry to ensure that the air was slowed down over many oblique shocks.
sr-71 engine inlet

On jet engines that don’t have such a complex inlet geometry as the sr-71, the best pressure recovery is mostly achieved by getting the primary oblique shockwave from the spike or inlet ramp, to hit the leading edge of the engine inlet, where it gets reflected as another shockwave.

As speed increases the primary oblique shockwave that gets formed on the spike gets shallower meaning that if you wanted to keep the shockwave of the mig-21 spike at the leading edge of the engine inlet, you need the spike to move forward as speed increases.


Why is the Boeing 747-300 not in service anymore? Doing a little doodling on flightradar24.com and Wikipedia, I saw that all the versions on the Boeing 747 except for the -300 version are used. Why is the Boeing 747-300 not used even though it is newer than the -100, -200, and SP versions?

The 747-300 was somewhat of a cross between -200 and SP. The -300 was almost same as the -200 except for the increased length of the hump. The -300 was never a success and was soon overshadowed by the -400.

The 747SP was the result of a requirement for longer range aircraft. Boeing engineers basically cut around 47' from the 747 fuselage in SP. However, by the time it flew for the first time, commercial air travel had changed (in no small part due to the high oil prices) and the model never sold as much as Boeing had hoped. However, when it was observed that there were no adverse effects when the rear of the cockpit lined up with the front of the wing, Boeing introduced the 747-300 with increased length of the hump with little else in terms of major change from -200.

However, just two years after -300 was introduced, Boeing introduced the -400, which was a significant improvement- it eliminated the flight engineer, increased range among others, while retaining the -300's hump (which meant more economy seats). 747-400 is the most successful model of the series, with more than 690 orders. Most airlines jumped straight to the -400, effectively killing the -300.

Actually, the 747-200 production (with over 390 made) ended after the -300 version (of which only 81 were made). So they are more of contemporaries.

Also, it'll be a stretch to call that the older 747 versions are still in passenger service. 747-100 is not flown with passengers anymore, current operations of 747SP hardly qualify as passenger service and the most successful of these, the 747-200s are also being slowly phased out, if you discount the VC-25s flying around with US President (which are slated to be replaced by 747-8s).


How to literally take the wing off a single engine Beechcraft-style airplane? First off I do not want to do any kind of maintenance. I was driving past an auto junk yard and saw they have half of a low wing, maybe a Beechcraft, airplane and I would like to try and buy the wing for a table or some type of project. I would like to know what kind of tools required to do such a task other than a sawzall!

A normal collection of combination wrenches and sockets, in inches, plus pliers, wire cutters etc, the ole' help along hammer, small bolt cutters for cutting control cable, etc. should do the trick.  Maybe sawhorses to rest the fuselage and wing on.  If the wings are individually removable, they'll be attached with two big bolts or two rows of smaller bolts, just inside the cabin under the seats, and a singe bolt at the back on each side.

The main thing to take care with is there'll be a hydraulic line running out the wing root to the landing gear leg with red hydraulic fluid (similar to ATF fluid) in it for that side's brake, so you should disconnect at each end and drain the brake line first, and there is probably a fuel tank so you need to make sure that is drained and be ready to catch fuel when you disconnect the fuel line connection at the fuselage.   If it's been sitting there for years the fuel is probably all gone but best be ready just in case.  Bring along a fire extinguisher while you're at it.

It's not much different than cutting up a car except the metal is easier to hack at if you want to take the sawzall to it.


Is it possible to tilt a propeller for attitude control, similarly to jet thrust vectoring? Are there examples of propellers tilted in a controlled way to help in attitude control for pitch and yaw, adding a torque component?

Tilted propeller assumption

This would be similar to thrust vectoring in jets.

Vectored thrust principle

Alternatively could a swashplate similar to the one used in helicopter main rotor be used to generate asymmetric thrust?

(I think this excludes convertiplanes where the propellers are converted into rotors to take-off, land or move vertically.)

Yes, on airships.

The Zeppelin NT can rotate its two forward and one rear propellers to create lift instead of thrust, a capability of particular value when the airship descends in an atmosphere with a strong temperature gradient. From this page about the Zeppelin NT:

  The two forward propellors swivel to 120° and the aft one to 90°, and
  a fixed aft lateral propeller give a high level of manoeuverability,
  and enable smooth, quiet flight and impressive fuel economy. Some of
  the unique flight characteristics come from the swivelling propellers,
  like vertical take offs, precise landings, hovering over exact
  locations, turns on its axis and flying backwards.

Tail propellers of the Zeppelin NT Airship. While the sideways mounted propeller is fixed, the rear propeller can swivel through 90° (picture source)

Front view of the Zeppelin NT with the forward propellers tilted up (picture source)

Another example would be the V-22 Osprey, obviously, but you might prefer to call those whirly things rotors, not propellers.


Can radars detect small drones? I've just started working with weather radars and such. With weather radars, it is possible to detect bird migrations with a specific algorithm and a lot of information about birds, but it would be a problem to detect a single bird (depending on the bird size) because of the radar's resolution.

I am wondering, if you have a place or a secret base that you don't really want the population to see whats in that area and take photos of the inside of the area or spy, is there a way to detect small drones with radar signals if you pack a few radars around your place or military base? If so, how?

Depends entirely on the drones. If the radar system is known and the drone is designed not to be detected by this particular radar system, then the drone can only be detected in exceptional circumstances. Small size would be one way, but in order to be effective, big is better.

Detection has many aspects, and one of them is how soon detection happens. If all you need is to stay undetected while you approach the target, only the frontal aspect needs to be considered. If, however, you want to stay undetected for the whole mission, the task becomes much, much harder.

The radar systems in operation during the Eighties along the Iron Curtain could already detect single, large birds. Adding computerized signal processing and networking of several radar stations has improved detection performance many times over since then. See this question for more details.


Can thermals or high density altitude improve fuel efficiency? Suppose a pilot is just cruising around building flight time. In order to get the most flight time for fuel, would flying on a dry cold day or on a hot thermal filled day save fuel?

For flight time and saving fuel, the density is not relevant. Density is relevant to distance covered if you need a set cross country distance rather than a set time. You would only want to set power to maximum endurance which will be very near best glide CAS, while best true airspeed and ground speeds would change with density the best endurance CAS would not.
It may also be advisable to plan relatively shallow descent angles so that the engine stays within a reasonably efficient power range. Climb with power low enough that you can keep it leaned.(after the initial takeoff and climb out, unless maybe you are at an excessively long desert runway)
Thermals could aid the flight time allowing even lower throttle settings but could also harm as they go both up and down, capturing the right current depends on the pilot's glider experience.
Now where I rent, fuel is included in the per hour price and the goal is usually to get a set distance or set of maneuvers in a minimum time. Just the opposite of what you propose.


What should be done in case of the avionics failure? Yesterday I was flying in my simulator with the Cessna 172 when I thought about simulating a fault in the plane's electrical system (alternator and master). But then I was in doubt, if I can't contact the tower or enter a code on the transponder, how can I inform that I need to land on a runway?

In the U.S. (other jurisdictions may be similar)...

Avionics are a convenience in VFR day flight. You should be able to fly your airplane by sight picture alone. There are aircraft flying today without any electrical system at all. In a fixed-gear aircraft, none of the equipment required by Part 91.205(b) require electric power. There are standard protocols in place if you have to fly to a destination without electric power.

If you are not on a flight plan or flight following when you lose electric power, stay clear of Classes A, B, and C airspace as well as the 30 nautical mile mode C veil around Class B airports, and the airspace above Class A, B, and C. Stay or descend below 10,000 feet MSL if possible or 2500 feet AGL when not possible to descend below 10,000 feet MSL.

If you lost all electric power before communicating your situation and intentions to ATC, you can assume that squawking 7600 on your electric transponder will do no good, either. Find a VFR Class D, E, or G airfield where you can land. Land as soon as practicable. Remember, you can not enter Class D airspace (normally a 4 mile radius from the field) until you have established two-way communications with them. You can, however, circle above the traffic pattern or tower at an altitude outside of the usually 2500 foot AGL ceiling of Class D until you get light gun signals from the tower. Wagging your wings or following their instructions will be your acknowledgement of light gun signals. Two-way communication will then be established.

Remember, an active IFR plan will give you clearance to your declared destination or declared alternate(s) at your ETA. Neither a VFR flight plan nor flight following prior to an expressed clearance will give you clearance into A, B, C or D airspace.

You should follow this plan of action at any Class D, E, or G airport with an operating control tower. Typically (but not always), a Class E or G airfield will not have an operating control tower. At those airfields, follow the AIM recommendations for entering the traffic pattern for a landing. An overhead flyover well above traffic pattern altitude would be advisable beforehand. Be very cautious of existing traffic. And, make your flight path as predictable to other pilots as possible. Although communication is strongly recommended, it is not required.

If you are flying on an IFR flight plan in IMC, follow the directions of Part 91.185.

If you are flying VFR at night, make it a habit to have the phone numbers of nearby towers, TRACON, and ARTCC in your cell phone. Call them to tell them of your predicament. Declare an emergency via cell phone. Then, use your Part 91.3 PIC authority to request clearance to land at any airport where the runway lights will be lit regardless of airspace or class. ATC can coordinate your clearances, then call an airport official or radio a passing airborne aircraft to turn the light on for you. You won’t be able to do it yourself without an operating radio. And, landing at a dark airport without a landing light will be challenging at best.