Why is EASA CS 25 non-binding? EASA states that Certification Specifications (e.g. CS-25) is non-binding on their website. See the regulations structure PDF.

Each Part to each implementing regulation has its own Acceptable Means of Compliance and Guidance Material (AMC/GM). These AMC and GM are amended along with the amendments of the regulations. These AMC/GM are so-called ‘soft law’ (non-binding rules), and put down in form of EASA Decisions. A comprehensive explanation on AMC in form of questions and answers can be found on the FAQ section of the EASA website.
Furthermore, Certification Specifications are also related to the implementing regulations, respectively their parts. Like AMC/GM they are put down as Decisions and are non-binding.

The FAA's 14 CFR 25 is certainly what I would interpret as binding or required. As a manufacturer you are required to show compliance to applicable parts of 14 CFR 25.
What does EASA mean then? Or what are they trying to communicate about Certification Specifications such as CS25? Or what is different about their organization that makes CS-25 “non-binding”?

The reason is that EASA cannot provide legally binding interpretations of EU Regulations, and the Certification Specifications are an interpretation of the EU Regulations.

Within the European Union (EU), legally binding interpretations of the EU regulations are exclusively provided by the national and EU courts and the European Commission.  The EU Member States are responsible for interpreting and implementing EU law in their national legal system.

The European Commission (EC) has created the European Aviation Safety Agency by decision EC 218/2008, recently repealed and succeeded by EU 2018/1139. The EC tasked EASA with creating certification specification and other material:

  EU 2018/1139, Article 76

  ...

  The Agency shall, in accordance with Article 115 and with the applicable delegated and implementing acts adopted on the basis of
  this Regulation, issue certification specifications and other detailed
  specifications, acceptable means of compliance and guidance material
  for the application of this Regulation and of the delegated and
  implementing acts adopted on the basis thereof.

And thus EASA is tasked with creating certification specifications that allow application of the high level EU aviation safety regulations, which requires of course the interpretation of those regulations.

At the same time, they don't have the power to give a legally binding interpretation, because that is reserved for the national and EU courts and the EC.

Consequently the Certification Specifications published by EASA that give the required detail to comply with the regulations, are not binding. They are referred to by EASA as "soft law", whereas the Regulations and Implementing Regulations on which they are based and which are published by the EC are referred to as "hard law"

As an aircraft manufacturer, you may argue that there are alternative ways of complying with the EU aviation safety regulations (hard law), whilst deviating from the Certification Specifications (soft law). If you make your case well, you will still get a type certificate.

This is not any different in the US, where aircraft can be certified with deviations from FAR 25. You don't necessary need to show compliance with all of FAR 25, if you can convince the FAA that the deviation from FAR 25 is reasonable and safe, a type certificate will be granted.

For example, see this table of granted exemptions from FAR 25 for the Boeing 737-8 and 737-9:

source: 737 type certificate(PDF)

Relevant EASA FAQ's:

What are the areas of responsibility for the Agency?
What is the definition of an IR, AMC and CS and GM and what differences can be proposed?


What did Fiji have to do when it incorporated GPS into its aviation system? I'm reading the BBC's How Fiji changed the way we travel; The little Pacific island nation was the first to incorporate GPS into its aviation system – and in doing so forever changed the way we get from Point A to distant Point B..

The article (and photos!) are quite interesting and worth a read. I'll quote just one paragraph below:

  Fiji approached the US and its Federal Aviation Administration (FAA) to volunteer as the testing ground for GPS navigation. The FAA agreed to fund the upgrade, supplying equipment and technical support in return for the knowledge it could take away from the trial. It would take well over a year to get the system ready; in addition to the installation of the equipment, new flight routes had to be charted, manuals developed and pilots and crew trained.

and later:

  Fiji proved that GPS could improve aviation in myriad ways, making it faster, more efficient and safer. In the quarter century since Fiji adopted GPS navigation for its domestic flights, the technology has been adopted around the globe, often with the direct help of Fiji’s new experts.

I'm having trouble understanding what exactly Fiji did when it "incorporate(d) GPS into its aviation system". Does this refer to installing GPS receivers on domestic Fiji Airways planes and training only, or were there any hardware or procedural changes on the ground as well?

This early ICAO document covering the introduction of GNSS (GPS) should cover the whole topic quite well. I would skip to section 3 (page 75) Information on Fiji’s Early Application of GPS Technology. But the highlights are effectively:

  Fiji consists of 300 islands (mostly volcanic) scattered over 200 000
  square miles of ocean. Of these, only 100 are inhabited. There are
  nineteen airfields, plus seven that are privately owned, but only five
  of the nineteen have NDBs and one has VOR-DME. This means that 80 per
  cent of the area is without any form of navigation aid. There are also
  helicopter and seaplane operations. Navigation has been accomplished
  primarily through visual flight rules or dead reckoning.

  ...

  Fiji became involved in FANS and GPS in 1990/91 through briefings given by CAA Australia, and became
  convinced of the safety and cost benefits to be gained. Ad hoc trials, including long distance oceanic flights with a
  hand-held GPS receiver convinced Fiji of the potential of the GPS.

  ...

  Under a Memorandum of Co-operation (MOC) the United States FAA provided equipment and operational and
  technical support to carry out trials and demonstrations. GPS receivers were provided for installation in all domestic
  IFR aircraft. These early receivers were not certified, and special procedures were developed to ensure that all the
  information provided by the GPS was confirmed by other navigation sources.

  ...

  Some of the main features are listed here.

  • GPS routes had been designed to all nineteen aerodromes. The GPS route charts show GPS airways and GPS
  way-points at the intersections.

  • GPS checkpoints were established and surveyed on all the aerodromes, initially using a GPS receiver but
  now these have been resurveyed by an outside contractor to WGS-84.

  • Outside areas of VOR/DME coverage, the pilot DR is now replaced by GPS procedures.

  • Cloud break procedures were also designed to enable pilots to descend below cloud and make visual contact
  with the island, so that in most cases they leave a pilot at 1 000 ft above obstructions, five miles out, on the
  extended centre line. This information together with way-points were entered into the GPS receivers via data
  cards, by the CAA Fiji.

  • Pilots and controllers were trained and examined on the rules and procedures. Pilots also had to undergo a
  practical test before being approved and pilots may not use the GPS unless they are approved.

  • Based on this initial experience, the charts have been further simplified so that pilots can now select, on the
  GPS receiver, straight-in approach or cloud break, when this was needed.

This early 90's advertisement for Trimble GPS units also makes claims to being the ones that were used on these first approaches.

According to the document Fiji basically moved everything over to GPS; en-route navigation, approaches, the whole shebang. This helped them fly safer in IFR and have way more coverage than their limited ground based beacons gave them. The US helped not only create procedures, plates and information but also equipped all Fiji based operators and airfields.


These "FICON" NOTAM's contractions aren't in the FAA contraction list. What do they mean? These NOTAMs for KSGF state "Snow" when the icon on the left is hovered over with a mouse.  The contraction "FICON" does  not appear in the Notam Contractions list.

It is currently the middle of June in nearby Oklahoma, and it is hot here, so a NOTAM related to snow doesn't make any sense.

What are these NOTAMs telling us?

FICON is outlined in FAA JO 7930.107 "FICON REPORTING".

FICON is the "FIeld CONditions reporting. It identifies information that used to be called "braking action", but is now a little more succinct.

The conditions for the runway are reported in thirds, [First Third]/[Middle Third]/[Last Third], with the following data outlined on page 6:

So 5/5/5 means that the runway is covered with frost or is wet and is "damp or 1/8" or less of standing water". Pilots used to report this as "good" braking action.


How do pilot and copilot operate and coordinate the radio? How do the pilot and copilot of a large commercial jet operate the radio when talking to ATC? Is there a push-to-talk button, or some voice-triggered mechanism?

Also, how do they coordinate it? How do they decide which pilot should be talking to ATC?

Both yokes have PTT buttons. Generally one person is in charge of the communications. In military aircraft that is often the task of the navigator in twin crew airplanes. I would think it generally falls on the pilot not flying the aircraft although both should be listening to the instructions.

The switch is on the front of the yoke (reverse side from what the pilot sees) and is generally triggered with the left index finger. Here is a pic from a yoke for reference. Note the button on the left upper part labeled "mic".

source

I have never seen it (but then again there are many radios I have not seen) but some radios may have a VOX (voice-operated transmit) option which would bypass the PTT. This however would be very irritating on the channels since there are lots of planes on a single frequency talking to the tower.


How to decode ARINC 429 data? I am looking for some help regarding decoding ARINC 429 data.
I have a CSV document that contains sequentially stored ARINC 429 labels.

My overall goal is to be able to scan for 4 specific labels and only decode those frames (data field, label field, and ssm field) and append them to the document.

Does ARINC 429 randomly come in different data formats (i.e. BCD, BNR, Discrete Bits, etc)?

Since I am looking for specific labels, is it okay to only have it set to decode BNR format or do I need to be able to identify and decode all the data formats?

ARINC 429 is a defined standard that not only describes the packet structure (32 bits) but also the data formats for different labels depending on the equipment ID. To know how to properly decode an ARINC 429 label you need to know the Equipment ID, which can then be used to look up the meaning of a specific label.

The manufacturer of the device that the data came from may also provide the definition of any non-standard/custom labels

If you know which labels you are looking for you don't have to decode the entire label, you just need to inspect the bits 8-1 to determine the label.

In general though, the ARINC 429 specification provides a guideline for labels:

  Binary coded decimal (BCD) sub-group 001 to 067, 125, 165, 170, 200, 201,230 to 237.

  Binary (BNR) subgroup 070 to 124, 126 to 144, 150 to 154, 162 to 164, 166, 167, 171 to 177, 202 to 227, 240 to
  257, 262 to 265, 267, 310 to 347, 360 to 376.

  Mixed BCD and BNR subgroup 260, 261

  Discretes subgroup 145 to 147, 270 to 276

  Maintenance and discrete data subgroup 155, 156

  Maintenance data subgroup 157 to 161, 350 to 354

  Test word subgroup 266, 277

  Application dependent subgroups 300 to 307

  Acknowledgement subgroup 355

  Maintenance ISO #5 subgroup 356

  ISO #5 message subgroup 357


Is there a comprehensive source for aircraft specification data for most of the aircraft in the world? I'm aware that I can look at the Wikipedia entry for an aircraft and discover specifications like the MTOW, length, cruise speed, etc. However, I was wondering whether there is a (preferably free) source of all this data combined for most aircraft. Does such a data source exist?

You can find a lot of information about aircraft in their Type Certificate Data Sheet that is available from the FAA or other certificating authorities. The FAA's is located here. It takes a bit of time to find certain things, and other things aren't included like range, or sometimes dimensions.


How can I figure out the take-off minimum when multiple minimums are listed in the TPP? For example:

If the published take-off minimum depicts:

  Standard with minimum climb of 565' per NM to 2800, or 1000-3 with
  minimum climb of 370' per NM to 2800, or 1500-3 for climb in visual
  conditions.

How can I figure out which of the various minimums apply? For example, if the airport has 1200-6, which of the available take-off minima can be used? Could you explain in detail and why?

(this answer is specific to the USA and FAA rules. Other countries may be the same, or similar, but I'm not familiar enough with them to guaruntee that this answer can apply outside of the USA)

To answer your question, we must first define what a "Standard Takeoff Minimum" is. Part 91.175 defines the standard wx conditions required for takeoff for commercial operators on an IFR flight plan:

  §91.175 Takeoff and landing under IFR. (f) (2) (i) For aircraft, other than helicopters, having two engines or less—1 statute mile visibility. (ii) For aircraft having more than two engines— 1⁄2 statute mile visibility.

Notice that there are no cieling requirements, only visibility. One- and two-engine airplanes must have 1 mile of visibility, and airplanes with 3 or more engines require 1/2 mile visibility.

Non-Standard - Some runways have obstacles in the distance or, for other reasons, require the weather to be higher than "standard" in order to use that runway during low visibility operations. These non-standard" minimums are published in the TPP. These minimums might be visibility-limiting only, or they might require both a minimum visibility as well as a minimum ceiling.

Ok, so that gets us to your question, in which you have provided specific examples.

  Question: If take-off minimum depicts "Standard with minimum climb of 565' per NM to 2800, or 1000-3 with minimum climb of 370' per NM to 2800, or 1500-3 for climb in visual conditions."

Standard with minimum climb of 565' per nm to 2800. This means that if your aircraft has the capability to climb at a rate of 565 feet per nm all the way to 2800 feet MSL, then you can use "standard takeoff minimums", which is 1 mile viz for 2 engines or less, or 1/2 mile for 3 engines or more, as long as you maintain that climb rate all the way to 2800'.
or 1000-3 with minimum climb of 370' per NM to 2800. If your aircraft cannot maintain the climb performance listed in #1, but you CAN maintain a 370'/nm rate of climb, then you can takeoff when the weather conditions are 1000-3.
or 1500-3 for climb in visual conditions. If you cannot maintain either of the two previous climb-out requirements, then you must takeoff in visual conditions and the weather observation must be a minimum of 1500-3

  Question: If the airport has 1200-6, what take-off minimum can be used?

In this case, you have a visibility of 6 miles, which is higher than the minimum visibility requirements for all 3 items listed above.  But you also have a ceiling of 1200 feet, which would prevent you from using Item #3 (due to the minimum ceiling requirement of 1500).

If your aircraft has the performance capability to meet either Item #1 or #2, then you have legally met the minimums and can depart.

  IMPORTANT Follow-On

The above information is only applicable to commercial flights operating under Parts 121, 125, 129, and 135 rules.  "Takeoff Minimums" do not apply to flights operating under Part 91 rules.  A part 91 flight can legally depart under 0-0 wx conditions. (although it is generally considered unsafe to do so, and several arguments have been made that it might be a violation of the rules to "operate safely"


When were airbrakes used for the first time in aviation? I would like to have some information about the history of airbrakes.

(Flight magazine 1914)

I'll answer the title question, as the complete history is too broad. That would be the Avro Scout (model 511) of c. 1914. Only one was built. Yes, that suspiciously looks like flaps. Back then +100 years ago that invention was called an air brake, flaps are air brakes after all.

From Wikipedia:

  Most unusually for its time, the inboard lower wing featured landing flaps air brakes, so the 511 landed at a sedate 35 mph (56 km/h).

This is what the plane looked like:


What are the pros/cons of all-moving rudder? All-moving flight control surface (stabilator instead of a stabilisator+elevator) are common on supersonic aircrafts but this is usually used for pitch control only. For rudder, this design (one all-moving piece instead of 2 separated pieces, the rear one being the one moving) is not common. The only example I think of is the SR-71. What are the reason for adopting this all-moving rudder on the SR-71? Why is it not spread? In short, what are the pros and cons of all moving control surface for yaw control?

All-moving control surfaces are like regular surfaces, only that the moveable part extends over 100% of the chord. Since the effectivity of a control surface grows with the square root of the chord fraction $\lambda$ of its moveable part, an all-moving (also called full-flying) control surface has twice the effectivity (defined as normal force change per degree of movement) of one with a 25% chord length of its moveable part.

Effectivity of a control surface over chord fraction $\lambda$

Hermann Glauert was the first to calculate the inviscid lift due to control deflection, and the result of his work is shown above. The truth (as defined by wind tunnel results) is somewhere between his curve and that of my simple approximation.

Control surface in subsonic flow

Deflecting a flap causes the camber of the control surface to change. This is a positive effect in subsonic flow and allows the resulting airfoil to create more lift in the desired direction. Also, the orientation of the leading edge is maintained, causing much smaller suction peaks there than when the full surface is deflected. Suction peaks require a long pressure rise, which promotes flow separation when its gradient is too steep.

Control surface in supersonic flow

In supersonic flow, camber increases wave drag, so the full-flying control surface is more effective. Pure supersonic flow has no suction peaks, and flow separation is less of a concern. Therefore, full-flying surfaces are better for supersonic flight, while hinged surfaces are the better choice in subsonic flow. Especially in transsonic flow, at least a moveable stabilizer is necessary to avoid control reversal due to the contour break of a hinged control surface.

Stealth aircraft

Stealth aircraft benefit from large, coherent surfaces, and the gap of a control hinge will increase their RCS. Even subsonic stealth aircraft like the Lockheed F-117 and the Northrop Tacit Blue use full-flying control surfaces for their ruddervators, as does the supersonic Northrop YF-23.

Why the SR-71 rudders are special

An intake unstart at Mach 3.2 is a violent event, and the SR-71 needed all the yaw control authority available to compensate for the sudden asymmetric loss of thrust. Its rudders were optimized for supersonic use, and the actuator could be driven to its extreme position by an explosive charge which was fired automatically when an intake unstart was detected. To ensure optimum intake operation, the engines were positioned at mid-span, and the yawing moment of thrust changes was much higher than that of conventional fighter aircraft which have their engines close to the centerline for better roll agility. In addition, they use their rudders mostly in subsonic flight; only the size of the vertical tail is determined by yaw stability at top speed.


How to determine climb performance for various flight speeds? I have the following climb performance chart:

and I need to evaluate the maximum rate of climb in different flight conditions.
The problem is, this chart is valid only for 85KIAS. Is there a way to evaluate the maximum rate of climb for other flight speeds, given the RoC and climb gradient @ 85KIAS?
edit: The zero-lift drag coefficient and aspect ratio of the aircraft are given. And it is not important if it is an optimum climb or not, I simply need to predict the maximum achievable rate of climb, given flight speed, altitude and aircraft mass.

Aircraft performance charts all work the same way. Unfortunately, this one only gives the climb speed at 85 knots indicated airspeed (KIAS).

To find the climb speed at different speeds needs more knowledge about the airframe. Then you can apply a simple approximation following this procedure.

The chart does not tell where on the polar the aircraft is. Will it climb better when flying faster or not? This is impossible to tell. Since you have only one speed and one power setting, but a range of masses, the aircraft will not be at its optimum climb setting for most points. We can make an assumption and declare the reference mass of 1700 kg as the point where the cited conditions are at the optimum. But then I would need at least the zero-lift drag and the aspect ratio to make further assumptions.

From the previous answer we take the climb speed equation $$v_z = \frac{v}{C}\cdot sin\gamma = \frac{v}{C}\cdot\frac{T-D}{m\cdot g}$$
and set the correction factor C = 1 for now. The resulting error is small at low speeds. Now we need drag and thrust.

First drag: The drag coefficient $c_D$ is approximately
$$c_D = c_{D0} + \frac{c_L^2}{\pi\cdot AR\cdot\epsilon}$$
with the known aspect ratio $AR$ and an assumed Oswald factor $\epsilon$ of 0.85. To arrive from here at the drag we need to multiply this with the dynamic pressure $q = ½\rho\cdot v^2$ and the reference area $S$:
$$D = ½\rho\cdot v^2\cdot S\cdot c_{D0} + \frac{(1700\cdot g)^2}{½\rho\cdot v^2\cdot S\cdot\pi\cdot AR\cdot\epsilon} = ½\rho\cdot v^2\cdot S\cdot c_{D0} + \frac{(1700\cdot g)^2}{½\rho\cdot v^2\cdot\pi\cdot b^2\cdot\epsilon}$$
when we substitute $AR = b^2/S$ with $b$ the span of your airplane. As I said before, induced drag depends on span, not on aspect ratio.

Now for the thrust. In a propeller aircraft power is constant and thrust is inverse with airspeed. Not indicated, but true airspeed, so we need to be careful. At sea level both are equal, and then thrust is straightforward: $$T = \left(½\rho\cdot v_{ref}^2\cdot S\cdot c_{D0} + \frac{(1700\cdot g)^2}{½\rho\cdot v_{ref}^2\cdot\pi\cdot b^2\cdot\epsilon} + \frac{5.5}{v_{ref}}\cdot1700\cdot g\right)\cdot\frac{v_{ref}}{v}$$

with $v_{ref}$ = 43.7278 m/s, which is 85 kts in sane units. The first two terms in the bracket look familiar: They are the drag contribution. The third term accounts for the climb speed of 5.5 m/s at the reference point in sea level altitude, so this accounts for the change in potential energy. If you need the thrust at higher altitudes, please correct $v_{ref}$ with the square root of the density ratio.

If those equations look daunting, continue solving for the climb speed:
$$v_z = \frac{v}{C}\cdot\frac{\left(D + \frac{v_{z_{ref}}}{v_{ref}}\cdot m\cdot g\right)\cdot\frac{v_{ref}}{v} - D}{m\cdot g}$$
$$v_z = \frac{1}{C}\cdot\left(\frac{D\cdot\left(v_{ref}-v\right)}{m\cdot g} + v_{z_{ref}}\right)$$


What does prevent air and fuel to be mixed upstream of the compressor? Why isn't fuel injected before the compressor or intake chamber?

The combustion chamber gets a lot of design and clever thinking to be able to mix fuel and compressed air in a short distance/space. This adds more weight and length to the overall engine.

I understand that changing that way of injecting fuel would need a new design and engineering to make it happen, e.g. to prevent blade corrosion, but nevertheless, could it be done?

If someone or a company did it already, and it didn't work, what were the reasons?

tl;dr The flame would progress upstream into the compressor until it and damage it, fatally disrupt the carefully balanced flow and stall the engine, or both.

long answer: In a turbine engine, there is a continuous flame where injected fuel is ignited by the already burning fuel downstream. Now you can't match the flow speed and the flame propagation speed exactly, because a small disruption could then blow out the engine and because both depend on the power setting in non-trivial way.

So in normal operation, the flame can propagate upstream until it gets to the point where the fuel is not yet sufficiently mixed with air to burn and there it stays. If you injected the fuel before the compressor, the flame would progress into it and as it would engulf the last stage, it would damage it and it would also increase the pressure beyond what the preceding stages could maintain, which would stall the compressor and cause the engine to stop, either immediately due to lack of oxygen, or by causing more damage with each stall cycle.

Note that spark-ignition (gasoline and LPG and CNG) engines usually do inject fuel before compression, but it limits their compression ratio to around 12:1 with high-octane gasoline, 14:1 with clever tricks. If the compression ratio was higher, the fuel-air mixture would ignite from the compression heat before the piston reaches the top-dead-centre and act against the rotation. In contrast compression-ignition (Diesel) engines have compression ratio at least 14:1 and inject the fuel only when it should start burning.

While early turbines had rather low compression ratios, the newest generation is getting into the range comparable with Diesel engines where the fuel might ignite due to the compression heat alone—they still use sparks for ignition, because the starter won't build up as high pressures in them, but it clearly shows they can't inject the fuel before it should start burning.


Is reverse thrust needed on a long runway Every time I have landed on a airplane reverse thrust is needed, but what if the runway is 18,000ft long. Because if the runway is longer couldn't you save fuel by not using the reverse exhaust

Reverse thrust is never needed.

A reverse thrust is relatively complex thing that can easily fail and for this reason when deciding whether an aircraft can land at some runway, the calculations are done without assuming reverse thrust. And of course the stopping distance for aborted take-off is also without thrust reverser, because if your engine failed, it won't provide any.

The reason to use reverse thrust is to reduce wear of the brakes and tires. The kinetic energy of the aircraft is huge and when it gets converted to heat in the brakes, they can get pretty hot. So if available, pilots always use reverse thrust to ease the brakes.

But it's not a big deal if not available. Thrust reversers are on MEL (minimum equipment list) for most if not all aircraft meaning the aircraft can be dispatched with thrust reversers inoperative. The brake wear will be higher from the more intensive braking, but it is better than having a plane wait for spare parts at some remote location.

Regarding long runways, there is almost always a possibility to turn off the runway earlier, which often saves time for the aircraft (shorter route to taxi) and makes the runway available for next aircraft sooner. So pilots usually still want to use some reasonable braking.


How do Flight Test Engineers plan and execute sortie profiles? Can someone from the field explain with a simple example the process of planning and executing a sortie profile as an FTE. Any reference books for an insight into the subject would be appreciated.

Three main factors influence the flow of a flight test sortie: data requirements, test point priority and flight efficiency.  For example, consider a test sortie that requires evaluation of stall handling qualities.

Data requirements specify which altitude, weight and cg, and configuration are required for each stall test point, for example.
Test point priority comes from the test team or test plan. One test point may be more important than others.
Flight efficiency refers to the need to minimize time between test points, minimize wasted fuel, and consider geographic position or airspace boundaries that may affect the test.

Balancing all of these things requires experience and judgment.  At the beginning of the flight, the aircraft is heaviest, so it makes sense to do test points that require heavy weight.  The second most important thing is to consider high priority test points. What points of high priority combined with heavy weight should be considered.  Finally, deciding the flight path that accommodates these two characteristics is the last factor.

This combination of judgment and knowledge and skill is difficult to describe accurately, and often two experienced professionals will come up with different, and equally acceptable, answers.


How much does it cost extra to fly with one additional passenger? How much does it cost to fly an airplane (like a Boeing or Airbus) when  there's one extra passenger there, at an average speed of 475–500 knots (880–926 km/h; 547–575 mph)? That is, about 100kg extra, including clothes and luggage.

I am basing the following calculations on the excellent answer by Peter Kämpf to this question: How much of an improvement would a 1% weight decrease on an airplane be to the industry?.

We can approximate the fuel usage with the Breguet equation

$$ m_\mathrm{TO} = m_\mathrm{Landing} \cdot \exp \left( \frac{R \cdot g \cdot b_f}{v \cdot L/D} \right) , $$
where:

$m_\mathrm{TO}$ is the total mass at takeoff
$m_\mathrm{Landing}$ is the total mass at landing
$R$ is the distance flown
$b_f = 0.000018 \mathrm{kg} / \mathrm{Ns}$ is the fuel burn
$v=250 \mathrm{m}/\mathrm{s}$ (about 900 km/h) is the velocity
$L/D=18$ is the lift to drag ratio

Assuming a fully loaded A320 (OEW $ = 42.6 \, \mathrm{t}$ with $ 19.9 \, \mathrm{t}$ payload and $3 \, \mathrm{t}$ reserve fuel $\Rightarrow m_\mathrm{Landing} = 65.5 \, \mathrm{t}$), we can do the calculation for the fuel ($m_\mathrm{TO} - m_\mathrm{Landing}$) with and without an extra 100 kg and compare for different distances $R$:

Note: this equation become increasingly inaccurate towards small distances because the takeoff, which uses more fuel, is not taken into account here.

Using the given speed, this can be converted to different flight times:

And by multiplying with the current jet fuel price of 616 US Dollars per metric ton, we get the additional cost of a 100 kg passenger per flight time:


How does the pilot control the Dassault Rafale? In the Dassault Rafale, how does the pilot maneuver the plane? I would expect to see a joystick centered between the pilot's legs. Instead, the Rafale has what appear to be two joysticks on both sides of the pilot. How does the pilot use these two joysticks to control the Dassault Rafale?

The  Dassault Rafale is one of the new generation of combat aircraft which have a side stick rather than a center stick for controlling the aircraft.

The Rafale follows the HOTAS concept- one where the buttons are placed on the throttle lever and the flight control stick allowing pilots to access vital cockpit functions and fly the aircraft without having to remove their hands from the throttle and flight controls.

There are two sticks in the Rafale cockpit on either side of the pilot. The one on the right of the pilot is the flight control stick and the other one is the throttle.

Image from freerepublic.com © Alex Paringaux/Dassault

The side stick controller on the right is connected to the aircraft computer and interprets the pilots input, which are then executed via various controls. The side-stick controller is force sensing with only a little travel, as can be seen in this video.

Rafale has a single throttle for both its engines- the left stick has more travel (compared to the other one) and controls thrust of both the engines through the computer. You can see both the sticks being operated in this video.

This type of arrangement is quite common in modern combat aircraft- both the F-35 Lightning II and F-22 Raptor use a similar arrangement- only difference is that in Rafale, the throttle and side stick look quite similar.


What happens if a pilot uses left rudder during a turn to the right? What happens if the pilot turns to the right using ailerons but then simultaneously applies left rudder? I'm asking about a large aircraft e.g. Boeing 747-800 or Airbus A380, or any other aircraft. If there are any negative effects, what mechanical or other measures are in place to avoid this (besides strict training)?

what mechanical measures are in place to avoid this?

The short answer is none.

Cross-controlling (the usual term for applying opposing aileron and rudder) is sometimes desirable.  Its greatest use in large aircraft is to align an airplane with the runway just before touchdown from a crabbed approach in a crosswind while keeping the upwind wing from rising. In other words, if you had a crosswind from the right and you were crabbed to the right to counteract it, just before touchdown you would apply left rudder to swing the nose left while applying right aileron to keep the right wing from coming up (or maybe put the right wing down a little).

  What happens when the pilot makes a right aileron turn but then gives a left rudder turn simultaneously

I'm making the assumption that you're talking about a turn not as part of a crosswind landing, and I suspect that your assumption is that pilots of large aircraft normally use coordinated rudder input when they use the ailerons. However, that is not the case. Once the aircraft is off the ground and absent any need to counter asymmetrical thrust from a failed engine, pilots generally take their feet off the rudder pedals and do not put them back on until short final. Yaw dampers or the equivalent for fly-by-wire systems take care of any adverse yaw ailerons may produce. Thus a cross-control scenario for en route flying would mean the pilot would have to make not one, but two errors. They shouldn't have had their feet on the rudders in the first place. Then they shouldn't have cross controlled.

But let's say that, for whatever reason, during en route flight, a pilot deliberately cross-controls once and then releases the controls. Generally speaking, that would not be disastrous. However, if they held a cross-control condition or kept repeating it in sequence, that's another story and would depend on a number of other conditions, and you could certainly come up with scenarios that ended in the destruction of the aircraft. Although I'm not sure the fly-by-wire airplanes would permit you to do that, but I've never flown any.

If you were in a 747-100/200 en route, you could if you wanted give it left aileron and right rudder in proportions that matched. In other words, the turning force of the ailerons would be cancelled out by the turning force of the rudder. The airplane would keep going straight ahead. However, you would be in a sideslip, and you'd have to increase the wing's angle of attack to keep from descending, which would mean more drag. Plus, there would be all that additional drag from the rudder. In other words, you'd be burning a lot more fuel than you should. Plus, you'll get a call from the purser asking what the hell is going on because gravity is no longer perpendicular to the cabin floor.


Our pilot lost the logbook Our company pilot lost the aircraft logbook for about 15 years worth of flights.  Boxes of stuff.  Who knows how he lost it.  We now want to sell the aircraft - can FAA reconstruct the logbooks?  If costs are involved can we get the pilot to pay for it?

We now want to sell the aircraft - can FAA reconstruct the logbooks?

As @fooot mentions in the comments you can find most of the details on this question here. There is a brief AOPA article here.

  If costs are involved can we get the pilot to pay for it?

For this you need to consult a lawyer (I would try and get one that specializes in aviation related cases). Depending on how his contract (if he has one) with your company is arranged you may have some weight here. There is a nice document covering a lot of cases in this space that you can find here. See section VI, but you may be covered for this under your insurance,

  VI. LOST, STOLEN OR DESTROYED LOGBOOKS
  MAY BE COVERD UNDER THE AIRCRAFT'S
  INSURANCE POLICY.

  Lost or destroyed logbooks may be covered under the aircraft’s
  insurance policy. However, whether or not coverage exists will depend
  on the language of the policy and, if the logbooks are not
  specifically covered under the policy, an insurer can deny coverage
  and a court may have to decide whether coverage exists.

I would seriously take time to look for them prior to doing anything as Im sure you already have. You can take a look at this thread for some info on rebuilding logs.

It is also worth reaching out the aviation shop that you use to maintain the plane. Many shops may have work records on file that can help you rebuild your records.


What are these numbers visible from the runway at Narita airport? At Narita Airport on the terminals there are big digital numbers visible from the runway. They aren't in some reliable order- I saw 98,91,93,95,97,99. Maybe they are Aerobridge numbers. I didn't get a photo as I only had my mobile which was off during taxiing. What are they for?

A good way to answer questions like this is to look at the Aerodrome Chart

As newmanth answered, these are gate numbers.

Using Google Maps, you can also see these numbers painted on the taxiway as a guide to taxiing pilots

If you want to understand airport air-side signage, one document I found useful is CAP 637 Visual Aids Handbook. It is a UK CAA document but I expect most of it applies in other parts of the world.

The CAA refer to stand numbers, as far as I know these are the same as gate numbers. They indicate parking positions for aircraft at airport terminals, these are places that allow for the loading and unloading of passengers.

Airliners arriving at airports will know what gate they have to taxi to, and ATC will provide them with taxiway routes. Airports provide signs so that pilots basically know where to find their allocated gate.


Airline safety: what happened between 1959 and 1962? The graph on page 17 (PDF page 18) of this Boeing air safety publication shows the fatal accident rate for commercial jets in the US and Canada dropped from about 40 per million departures in 1959 to 2 per million departures in 1962.  Since then, the rate has declined even further, but nothing as dramatic as the original drop.

What happened during the the 1959-1962 period to so greatly reduce the accident rate?

I believe the answer has something to do with the introduction of the passenger jet airliner, which first came into service in the late 1950s.  Note please that the original poster is asking for information on "commercial jets" whereas the statistics that others have offered have information on commercial planes in general, including prop planes.  I glanced at the statistics for 1959 presented above and there were only two passenger jets (including one KC-135, which you may discount if you like) that crashed.

Compare this to the statistics presented for 1962.  There were six or seven crashes of Boeing and Douglas jet airliners.

To me this means the differences were in all probablility not statistically significant.  We don't have enough "samples" to reach a valid conclusion.

What you can see is a general explosion in the number of people flying.  Jets really introduced the public to flying.


What is the cooling air exhaust velocity for the piston engine of a propeller driven aircraft? Piston engines of propeller driven aircrafts need to be cooled. There are engine cowlings which accomodate the inflow of air to "wash" over the engines within them and which is then exhausted out into the freestream.

The model in question here would be a single block engine in the cowling of a tracktor configuration propeller aircraft. The airflow enters the cowling, washes over the engine, and then exits into the freestream.

The question is:

What would be a good estimate for the velocity of this air stream exhausted into the freestream?

There are cases, as in the P-51 Mustang, where the cooling air adds to the THRUST of the aircraft as it is heated and expelled out the back of the air vent, much like a jet.  This actually added a few knots its speed.

There is always an issue of cooling as one scales up a fuel burning engine.  Towards the end of their time, piston engines for aircraft had grown exponentially in power in the race for performance.  This lead to major issues in cooling of engines such as the "corn cob" R-4360 Wasp Major.  Turbo or Super chargers also unavoidably raise the temperature of incoming air by compressing it.

So to estimate the velocity of the cooling airstream, one might begin a study of the principles of a jet engine.  Since no mass is added to the cooling stream and there is no compressor (as in a turbo jet, although prop wash may give some effect) the only considerations are ram pressure and thermal expansion of the cooling air.  Forward speed of the aircraft will be a major factor.

Study of the P-51 design may be a good place to start.


Is this XKCD comic list about autogyro features accurate? I recently came across this XKCD comic which gives you a number of facts about autogyros:

Image is copyright XKCD, licensed under CC 2.5 BY-NC

I'm not sure if this is satirical or really drawing attention to some very odd real-world facts, or a mix of the two.

Statements:

  Looks like a helicopter, but is nothing like a helicopter
  Flies like a plane but is nothing like a plane
  Cheap
  Needs a runway to take off, but not a long one
  Can land vertically
  Cannot hover
  Big blade on top is not powered […]
  Never stalls
  Sort of like a powered parachute
  […] usually homemade.
  Common in Europe. (I'm fairly sure I've never seen one in the UK)
  Can often be flown without a licence

Are these things all true? How do they actually work?

Flies like a plane.

To a certain extent in that the controls are plane-like, you do not have helicopter controls (no cyclic, etc.), but you also do not have wing control surfaces, so in some respects like a plane, but not exactly.

  Big blade on top is not powered.

True, the blades are unpowered; they rotate due to the wind. Some autogyros use power to rotate the blade to speed before take off, but the power is removed for flight.

  Never stalls.

You can put it into a stall attitude, but it self-corrects; it is basically a rotating parachute.The fatal mistake that pilots made with early autogyros was that when they entered stall conditions they instinctively pushed forward on the stick which resulted in the 'fuselage' tipping forward and the blades chopping off the tail. There have been a few fatalities this way.

  Sort of like a powered parachute.

Fairly good description. It is more like a powered paraglider than a helicopter or plane.

  Common in Europe (I'm fairly sure I've never seen one in the UK)

Maybe this should be more common in Europe. They are still uncommon in Europe, but they are more common in Europe than the US. Wallis Autogyros used to make them in the UK in the 1960s. Check out the Bond film "You Only Live Twice" for one in action (ignore the missiles, etc.; they are not standard fit on autogyros).

  Can often be flown without a licence.

Not in anyplace I have flown in Europe. The US may be different.


Who do I call to pick up my IFR Clearance at KBKL? I've had my IFR rating for ~2 years now, but haven't done much other than practice approaches to stay current. Flying to KBKL tomorrow, and when I depart to come back, I can't tell who I call to pick up my clearance.

The approach plates say "CLNC DEL 121.9 (when tower closed)" - okay, what about when the tower is open?

I've tried googling around, but the internet is filled with people asking how to pick up clearances in the air; I trained at a non-towered field so I've got the opposite issue.

Thanks!

Edit: Here's a link: http://airnav.com/airport/KBKL

When there is no separate Clearance Delivery frequency, just call on the ground control frequency to get your clearance.

Separate Clearance Delivery frequencies are only needed at busy airports to relieve radio congestion and work load.

Even at a "busy" airport sometimes you will see(hear) one controller work both Ground and Clnc Del when the workload is low.


Why does the Biot-Savart law give the induced velocity of a infinitesimal segment of a vortex filament at point P? My question is about the proof of how the Biot-Savart law can be used for vortex filaments. This is what I have in my textbook:

However, I'm not certain how it was derived - I understand that the Biot-Savart law originally came from electromagnetic theory, but could anyone present the proof for it's use for vortex filaments?

Intuitively though, something seems off - a vortex filament is just made out of lots of individual vortexes put together in a filament, so shouldn't the induced velocity at a point P of an infinitesimal section of the filament be zero unless $d\vec{l}$ and $\vec{r}$ are perpendicular... but clearly it's not the case,
$$
 d\vec{V} = \frac{ d\vec{l} \times  \vec{r} }{ \lvert \vec{r} \lvert ^3}
$$
, which is nonzero even when $d\vec{l}$ and $\vec{r}$ aren't perpendicular

Why would

  the induced velocity at a point P of an infinitesimal section of the filament be zero unless $d\vec{l}$ and $\vec{r}$ are perpendicular

?

The cross product in
$$
 \frac{ d\vec{l} \times  \vec{r} }{ \lvert \vec{r} \lvert ^3}
$$

does not change signs when going over the $\frac{\pi}{2}$ angle in between vectors, so the infinitesimal filament sections $d\vec{l^-}$ (immediately before $d\vec{l}$) and $d\vec{l^+}$ (immediately after $d\vec{l}$) have contributions to $d\vec{V}$ that do not cancel each other out. Therefore, $\vec{V}$ is not just a function of a single filament section, but of the entire filament, hence the integral.

If you check the next section in the source of your image, titled Straight-vortex case you will see this in action.


If an airline purchases an aircraft, do they have to/feel compelled to change the livery? If an airline purchases a used commercial aircraft, which would be painted in the livery of its previous owner, would the new airline ever be required (by law) to re-paint the aircraft in their own livery?

I am also curious what happens if a private individual were to purchase a used aircraft from an airline, again painted in their livery. Would they be allowed to fly it for some time still bearing the livery of the airline that used to own it?

If there is no law regarding this, then is there a general practice? I.e. most airlines would just keep the old livery until the airplane is due to be re-painted?

Yes - logos, trading names, liveries etc are all covered by trademark and you would need permission from the trademark owner to use them yourself. Besides, the schemes are good marketing so a commercial operator would want their own livery on it as soon as practical.


What is the benefit of having baro-VNAV in addition to a WAAS GPS? On Cirrus' 2015 aircraft page, they advertise Baro-VNAV capability in the new model. Having never done an LNAV/VNAV GPS approach (only LNAV or LPV), I'm wondering: when would I actually use it, if I already have WAAS and can just use the LPV approach? Typically, I'm used to seeing an LPV minima alongside any LNAV/VNAV minima. Are there exceptions? Is this feature valuable in practice?

LPV and non-baro LNAV/VNAV requires that a Space-Based Augmentation System (SBAS) be available to the GPS receiver.  In the United States, that system is called Wide Area Augmentation System (WAAS).  Similar services operate in other parts of the world (e.g. EGNOS in Europe, MSAS over Japan, GAGAN over India) but coverage is not worldwide, and not all GNSS (Global Navigation Satellite System) approaches are approved for LPV.

Having a baro-VNAV system in the aircraft allows you to shoot LNAV/VNAV approaches if SBAS is not available. While not as useful in the United States, as we have robust and reliable coverage with WAAS, it is nice to have in parts of the world where SBAS is unreliable or non-existent.

FAA fact sheet on RNAV (GPS) approaches: http://goo.gl/cIhIJa

Worldwide SBAS information: http://goo.gl/eooOau


When passing a waypoint, when exactly are we on the next leg? When performing one of the procedures shown in the pictures below, when exactly do we consider ourselves to be on the next leg?

For example: for the fly-by waypoint, when do we consider that we are no longer flying from the runway to Alpha, but we're now on the Alpha to Bravo leg instead? Is it in the middle of the arc, once we finish the arc...? For fly-over waypoints, I guess it's when we pass Alpha, but I'm not sure about that either.

The transition point as defined in RTCA DO-283 RNP MOPS is the point where the aircraft's path passes through a vertical plane that bisects the inbound and outbound legs going through the waypoint.

That generic description covers all the possibilities of the aircraft passing the waypoint regardless of how good or bad it is following the defined path.

Realistically, in the case of the fly-by waypoint, it's the point half way through the transition turn where the waypoint is directly abeam the flight path.

The same rule (crossing the bisecting plane) applied to the fly-over waypoint results in the transition occurring at the waypoint.


Why does the CF6 have a lower bypass ratio than the TF39? The General Electric TF39, which powered the original C-5 Galaxy, was the very first high-bypass turbofan brought into mass production, with a previously unheard-of 8:1 bypass ratio.  Yet, when it came time to make a civilian version of the TF39 (what would become known as the General Electric CF6), GE cranked the bypass ratio back to under 6:1 for the lowest-thrust version, and to 5.31:1 or lower for the beefier CF6s.

Why did GE decrease the bypass ratio of their engine, rather than increasing it further?

Increasing the bypass actually decreases the thrust. A good example is the CFM56-5B variant (sortable table on Wikipedia). The reason is easy to grasp, the more air bypasses the core, the lower the core's power.

The next question would be how did the TF39 achieve higher bpr and thrust? Through an extra half-fan and extra turbine stage. It will make sense by viewing the cross section drawing and front view below:

(flightglobal.com) CF6 top half, TF39 bottom half.

(wikimedia.org) TF39 front view.

This covers the thrust/bpr and the how, on to the why. The DC-10 (the launch CF6 customer) cruised at a higher Mach number (M0.82-0.88) compared to the Galaxy's M0.77. At high Mach numbers, a lower bpr is more efficient (think turboprop with a 40:1 bpr and a jet) -- speed is the key here.

Other reasons include the airlines' desire to have one fan with easy access, and fewer parts to deal with. Flight summarized it in 1969 as follows:

  General Electric CF6 in -6 form at 40,000 lb thrust for take-oft was the engine specified by American Airlines and United Air Lines in their launching orders for the DC-10-10. Whereas the TF39 has a large two-stage front fan assembly the CF6-6 has an entirely new single-stage fan with a small single-stage booster fan. The change brings down the by-pass ratio from 8.0 to 6.2 and permits the deletion of a stage from the compressor; take-off thrust is reduced from 41,000 lb (TF39) to 39,400 lb (CF6-6) but the cruise thrust/s.f.c. characteristics are improved at higher Mach. Other changes include fan blade containment built-in to the casing; substitution of a gearbox to suit airline requirements; control system adapted to airline practice (idle and reverse added); increased accessibility of fan and gearbox; external piping; and a review of all materials for increased life.

The beefier CF6 you mention -- the CF6-50 -- again increased the airflow reaching the core (which reduces the bypass air) by adding booster stages behind the fan. This is how to get higher thrust with minimal changes.

(flightglobal.com)


Before COVID, what was the largest aviation crisis ever? The Covid-19 pandemic is the worst crisis aviation has ever faced. Which one was the biggest one before that pandemic?

Crisis is somewhat hard to define explicitly but the September 11th Attacks had an enormous impact on the commercial aviation industry in perhaps more ways than the current Pandemic has.
It took nearly 3 years for aviation travel numbers to return after the attacks and arguably we are still seeing lasting impacts on changes to broad aviation travel procedures as a direct results of the attacks even 20 years later.


Which country is responsible for prosecution if a crime is committed over international waters? Theoretically speaking, let's say we're flying from Portugal to Cuba, on a Chinese-owned airliner. Whilst over the Atlantic, a crime is committed, and we land in the US.

Which country is responsible for prosecution? How is this determined?

Broadly the legal constructs that apply here are essentially the same as for sailing vessels - in other words when you're outside the jurisdiction of any given nation the laws of the country the vessel is registered in apply, and the captain is the one who makes the decisions.

More specifically once you enter the airspace of a nation that nations laws also apply (the same as crossing the boundary from international waters to the territorial waters of a nation - by entering their territory you're obligated to abide by their laws).

If the above doesn't seem murky enough, it's because it actually gets a lot more complicated than that when you start considering all the laws various countries may pass (and subsequently attempt to enforce).

Consider for example The "Special Aircraft Jurisdiction of the United States" in which the US claims jurisdiction over any aircraft in our airspace, or any aircraft in flight which is intending to land on our soil (as long as they actually do land on our soil).

As with most areas of international law going to far down this rabbit hole will likely lead to madness.
For practical purposes you can assume that four bodies of law will govern every flight:

The laws of the country from which the aircraft is departing.
The laws of any country whose airspace the aircraft transits, while in that airspace.
The laws of the country in which the aircraft is landing.
The laws of the country to which the aircraft is registered.

...and if you can avoid breaking any laws in those 4 categories you'll be pretty well covered for most circumstances.


Does a headwind/tailwind affect your rate of climb? I am still confused whether a head wind or tailwind would affect the rate of climb. Since in a HW/TW condition our a/c is basically still climbing in the same parcel of air, it is just that parcel of air is moving with or against our course hence increasing/decreasing the horizontal distance covered to get to the target height. This means that the time needed to get to the target altitude is not affected at all, but the horizontal distance is.

Yet my friends have been insisting that with a headwind an aircraft would climb faster to the target height, as the headwind helps create more lift by increasing the amount of air passing through the wings.

A steady (continuous) head wind (or tail wind) will not affect your climb rate, only your climb angle. It means you will reach a specific altitude in the same time interval, but your ground distance will be affected.

A head wind increase (as in a gust) will momentary increase your indicated airspeed, which you can trade for a (momentary) increase of climb rate. Similarly, a tail wind gust will temporarily decrease your indicated airspeed and you might have to pitch the nose down a little, to maintain airspeed and therefore reducing climb rate. These are only transitory effects, until the plane settles back to its original trim speed.


What does the "Caution" box mean on the sectional near Half Moon Bay, California? What does this Caution box on the sectional chart near Half Moon Bay, California mean? Is there an official reference for the meaning of this box?

This one is a bit confusing and interestingly there is nothing in the FAA's sectional guide on "Caution" boxes although they do appear on other charts as well.

This one in particular is a warning that you will need monitor the radio for the transition routes below 2000 ft. If you can zoom in or get TAC level map resolution you will see a different warning

(source)

If you note a bit south of half moon bay the chart makes note of the fact you should be using the TAC in that area:

(source)


Why can a Pilatus PC-24 land on unpaved and short runways like no other business jet? In 2013 Pilatus Aircraft unveiled their latest aircraft, the PC-24 light medium jet. On the website of Pilatus Aircraft they give several reasons why the PC-24 is better than any other business jet, the first two being

No other business jet can operate from runways as short as 2,690 feet (820 m).

No other business jet has been designed to operate from paved and even unpaved surfaces.

This sounds pretty impressive to me. But what’s different between a PC-24 and any other light medium jet on the market, which allows such short landing distances and the ability to touch down on unpaved runways?

Press picture from Pilatus Aircraft which shows the landing on an unpaved runway.

The Wikipedia page on the Pilatus PC-24 gives you some hints:

  The PC-24 is a twin-engine business jet, a larger jet-powered follow-on to the earlier Pilatus PC-12. It is considered to be a short takeoff and landing (STOL) aircraft, being designed to operate from short and rough airstrips. It incorporates an advanced wing design, with a large double-slotted flap system to achieve the necessary performance, having a stall speed of only 81 knots at the maximum landing weight. Pilatus has claimed that the PC-24 possesses performance attributes which are unmatched by any jet aircraft on the market. It possesses a takeoff distance of 820 m (2,690 ft) and a landing distance of 770 m (2,526 ft).

...

  The PC-24 is powered by a pair of Williams FJ44-4A turbofan engines. [...] The engines are mounted on the upper portion of the rear fuselage to prevent foreign object damage (FOD) during operations at rough airstrips. Other FOD-reduction measures include the enlarged flaps and chines on the nose wheel of the landing gear. The exhaust ducts of the engines feature an aerodynamic modification, having been shaped so the outflow contributes to the thrust vector during takeoff, reducing the takeoff roll distance.

So, in summary:

Advanced wing design with double-slotted flaps
Low stall speed
High mounted engines
Large flap and main nose wheel chines
Reduced take-off roll through vectored thrust
(Thanks to Peter Kämpf) Lower Wing Sweep to add effectiveness at low speeds at the expense of cruise speed.

There really isn't a lot that is going different from other business jets other than a shorter take-off/landing roll. The design isn't dramatically different, and it doesn't mention it but it probably has reinforced landing gear.

No production PC-24's have been delivered as of yet, so its hard to tell what they look like. The test PC-24's only have 150 hours behind them so they may not have had any rough-strip experience. It's difficult to say exactly what the modifications are because they may include other things like FOD deflectors on the wheels.


Why did this delta wing generate a lower Cl at a higher wind tunnel velocity? I'm an aerospace engineering student,and just did an aerodynamics lab in which we measured the lift & drag of a delta airfoil inside a wind tunnel between 0 and 40 degrees, in 5 degree increments, at two flow velocities (subsonic, M< 0.5). For some reason, the lift co-efficient is .25 lower throughout the entire curve in the higher velocity run compared to the lower velocity run, despite the drag co-efficient s being identical until the stall region (which begins at 30 degrees and completely separates at 35). Why is this? Considering the nature of the lab, this seems what I should be discovering. I have a theory that it has something to do with stronger vortices generated by faster flows, but wouldn't that INCREASE lift by dropping the pressure on top of the wing further?

In addition, another oddity: the L vs D curve increases SHARPLY between 0 and 10 degrees for both flows, but then the slope decreases after that and stays steady until the stall region. Why is that, and is that specific to delta wings?

The increase in the lift curve slope at low angle of attack is quite normal. At 10° you see the effect of vortex lift kicking in. Yes, that is specific to delta wings.

Attached and vortex lift over angle of attack (picture source). This is taken from the excellent Cambridge Core article on vortex lift and these particular diagrams are from E.C. Polhamus: A concept of the vortex lift of sharp-edged delta wings based on a leading-edge suction analogy, NASA TN D-3767, December 1966. They show lift over angle of attack, but lift over drag would look quite similar, also with a kink once vortex lift sets in.

The offset between the two speeds is harder to explain. This looks like an error in your angle measurement – there must have been different offsets between the two test runs. That there is an offset is obvious from the nonzero lift at zero angle of attack. Unless your delta wing had lots of camber, there should not be much lift at zero angle of attack.


DO-254 and microprocessors: how does it apply? How does DO-254 apply to commercial processors? For instance, I've noticed that "DO-254 certifiable" processors exist. Does that mean that these were designed with inherent redundancy?

DO-254 is for Airborne Electronic Hardware. Redundancy isn't necessarily required for DO-254. I would expect that the processor manufacturer would be able to provide a data package with the necessary documentation if a company were to use it in a DO-254 certifiable product.

In my experience, however, DO-254 is applied for custom micro-coded components only (for the FAA at least). DO-254 was a way to apply concepts similar to DO-178 to things like PLDs, FPGAs, and ASICs to prevent a "firmware" gap in certification.


Will the new Part 23 changes reduce the cost of avionics for existing aircraft? Will the part 23 changes coming in August help to reduce the cost of IFR GPS avionics? I'm looking to upgrade the IFR avionics in a 1978 Cessna 182.

Unfortunately not: the purpose of the part 23 rewrite is to make it easier to certify a new aircraft type (not individual avionics or other systems) and it doesn't apply to existing aircraft. AOPA has a good overview, including this (emphasis in the original):

  10. Are the performance-based standards applicable to all aircraft?

  No.  The new process of using performance-based standards is limited
  to new airplanes certified under Part 23, which would include
  airplanes with a maximum passenger-seating configuration of 19 or
  less, and a maximum certificated takeoff weight of 19,000 pounds or
  less.

To address the cost point directly, in theory if the part 23 rewrite creates additional demand for new aircraft, and if those aircraft use avionics that can also be retrofitted to existing aircraft, then the increased demand might reduce prices. But that's highly speculative.


What is the cause of cracking and corrosion in Trent 1000 engines? According to this description and this one of some Trent 1000 engine problems, there appears to be a problem with cracking/corrosion of the fan blades, but does anyone have any insight as to why this is the case? (And why this problem doesn't occur on other platforms?)

I was thinking it could be due to the composites used in the compressor fan blades, or perhaps something to do with the no bleed-air system unique to the Trent 1000, but I'm not entirely sure.

The problem is sulfidation corrosion, according to this article:
https://airinsight.com/rolls-royce-trent-1000-corrosion-issues/

Turbine blades are made of metal, and they suffer temperatures and forces so high that they are usually 'grown' from a single metal christal. A single blade can cost as much as a luxury car.

The problems also seem to be related. Corrosion leaves a little pit, which turns in to a crack due to the cyclic loads.


Can a non-instrument rated safety pilot log PIC during an IFR flight? The Scenario:
An instrument-rated private pilot files and flies IFR while accompanied by a non-instrument-rated private pilot who is otherwise fully certified and endorsed to act as PIC in that aircraft under VFR flight rules. While in VMC, the instrument rated pilot uses a view limiting device in order to practice IFR scan and procedures towards maintaining currency, while the other pilot acts as safety pilot. Both pilots meet all medical and currency requirements for the flight.
The Question:
Can the safety pilot in the previous scenario log as PIC that time during which he/she acted as safety pilot?
Note: This question differs from the question, How should time as safety pilot be logged?. This question is not answered there; this question concerns whether or not a non-instrument-rated pilot is qualified as required crew during simulated instrument flight in VMC while operating on an IFR flight plan, and whether that pilot is qualified to act as PIC in the given scenario.

No

The way that both pilots can log PIC is that the pilot using a view limiting device is logging PIC as sole manipulator and the safety pilot is logging PIC because he is acting PIC and a required crew member.

If the flight is operating under an instrument clearance then the acting PIC must be instrument rated. If only the pilot with the view limiting device is rated then he is acting PIC and is the only one eligible to log PIC. The safety pilot is also not allowed to log SIC as a required crewmember without an instrument rating while operating under IFR.

If you are in actual IMC then you shouldn't be logging anything and they other guy shouldn't be wearing a view limiting device.

If you want the PIC time ask your friend to fly VFR or get yourself an instrument rating.


How to get out of icing conditions asap? We all know certain weather can cause ice to form on an aircraft, and the danger it poses. Obviously the best way is to avoid flying near these areas in the first place.

Let's say I happen to fly into one. Aircrafts have de-ice equipment such as de-icing boots, pitot heat, engine de-ice etc; but sitting there and flying through the ice-cold cloud does not seem to be a good idea. So something must be done to get the aircraft out of icing conditions asap.

What is the best course of action? Should I descend at normal speed? Or descend and pick up speed? Climb? Perform a 180? Would a weather radar (which reflects precipitations) help?

well, you'd have to fly in whatever is the shortest route out of the icing conditions, obviously.
What that would be depends on your speed, wind, climb/descent performance, and how you entered icing conditions.
If you entered icing by climbing, diving may well get you out of it (but if you were climbing to avoid terrain...).
If you were turning left, turning right might do it (but were you turning left to avoid collisions?).
Etc. Etc.
IOW there's no universal answer, it's way too situational.


Is public data available for routes that enter/exit a certain airspace? I'm interested in air traffic density and flux (i.e., traffic that enters and exits) for the ZLA airspace. A good first pass would be flights that begin or end in ZLA (and that data is pretty easy to get from somewhere like OpenFlights, but that doesn't include routes like PHX-SEA, where a flight would pass through ZLA on its way from ZAB to ZSE. Is there any public information available about what routes pass through ZLA?

(Actually, I'm much more interested in the air traffic density and flux specifically for the Los Angeles metropolitan area, but I figure starting at the area control center level might be a good place to start.)

A free public resource would be the FAA's statistics page. I'm not sure if they have the specifics you need but they have a lot of data available. It would probably be easier to find data specific to the airports than it would for the whole artcc. Flight data doesn't usually include what airspace they pass through but where they depart and arrive.

There are commercial sites that have the raw data. FlightAware has full xml data for pretty much all scheduled flights going back several years. It's a treasure trove of data, it's a matter of extracting it. If you can write an api then  have options for using their data for a per-query fee. Their info page is here Their prices are in fractions of a penny, but I really know nothing about api's so I have no idea how quickly they would add up. It probably depends on how efficient the api is in getting the information with the least number of queries.


Why safe take off weight exceeds the safe landing weight? This looks contra-intuitive: if a plane can take off and fly horizontally, what prevents it from descending and touching down to the runway with the required small vertical speed?

Because when taking off you go from 0 vertical speed to a positive rate of climb all by way of the wings (the force on the gear will decrease over time to 0 when airborne). But while landing you will go from negative rate of climb to 0 vertical speed. Most of that will be absorbed by the gear (the force on the gear will spike and then settle to only the weight of the aircraft). After touching down there is also the braking force exerted on the gear which is proportional to the mass of the aircraft.

It is that spike+braking force that the engineers are worried about when calculating max landing weight.


Why aren't passengers instructed how to lift aisle armrests? Only when I chanced on this /r/LifeProTips post, did I know

  Most airplane aisle seats have a small lever or button on the underside of the armrest, near the hinge. Pushing or sliding this lever will release the hinge lock, allowing you to raise the armrest.

When horizontal and down, aisle armrests  obviously hinders exit during emergencies when  saving seconds can save lives, especially for more obese passengers. So why isn't this hidden button/lever disclosed to passengers, like in the mandatory safety briefing or video?

I'm not asking about armrests between seats that don't require a hidden switch to lift.

The FAA provides some useful links in their cabin safety index document here. It seems according to this document, as well as this bulletin arm resets (in general) may actually provide a bigger safety risk when lifted and that they should be placed in the down position for takeoff and landing for emergency reasons:

  3-3484 PROTRUDING PASSENGER SEAT ARMRESTS. Inspection of the Hardman Model 9500 and other passenger seats installed on several
  aircraft disclosed that the armrest in the upright or stowed position
  can protrude approximately 45 degrees aft the seatback. In the event
  of an emergency evacuation, protruding armrests could present an
  obstacle between seat passageways, obstructing emergency exit access.
  Air carriers should emphasize to F/As that prior to takeoff and
  landing they verify that the armrests are in the normal forward/down
  position in order to ensure that they do not obstruct the passageway
  between the row of seats leading from the aisle to the emergency exit.

Also it would seem that according to §382.61   What are the requirements for movable aisle armrests? the movable arm rests are mainly there to allow the easier seating of those with limited mobility and not intended to aid in evacuation.


Why can't blimps be economical for commuter / public transportation? I dont know what the net load is for a blimp, but if they could somehow carry 100-400 people, why coudln't they be used like ferries in metro cities like SFO and NYC? Even if they could only scoot at 60-100mph, they can cut clean across waterways and save a ton of time for commuters while (seemingly) being more efficient than fixed-wing aircraft as well as safer (engine failure? gently float down and call for help).
A bonus would be if they could convert their balloon into a flying wing shape in flight via compressing the gas, reducing volume, and having it fold into a wing-shape allowing them to increase speed. If they could get near 200mph, that could open up decent commuter service between LAX <-> San Diego. But even 60mph could connect the greater Los Angeles area. If the weather were bad, a cable-tethering system could be used to guarantee smooth landings (fly into the tether, grab it, command the cable to retract, thus pulling the blimp into the station).

I'm guessing that it would absolutely be possible to make blimps economical. The question is whether it would be better than alternatives.
For public transportation, there are a number of common alternatives:

Buses. Low-to-medium throughput, relatively low speed, short distance, very high flexibility.
Trams. High throughput, relatively low speed, short distance, high flexibility.
Metros. Very high throughput, medium speed, medium distance, medium flexibility.
Planes. Medium throughput, high speed, long distance, medium-to-low flexibility.
Ferries. Medium throughput, relatively low speed, situational (i.e. water connections).

(There's also regional coaches and trains, which are the big brothers of buses and metros. Omitted mostly for brevity.)
The challenge for blimps would be to out-compete any of these other forms of transportation. It would be impossible for a blimp to cover the very high throughput offered by metros or trains, or the flexibility of buses. For larger distances, planes are much faster and are not nearly as affected by weather. They also have the benefit of trained personnel/drivers (mostly) readily available, more infrastructure, production and we know that they work. Plus you don't have to change people's habits, which is hard.
In short, there is nothing a blimp could offer that isn't already covered by better alternatives. Except maybe a nice view on a sunny day.


How airlines select new Captains...? How does an airline select Captains for a new but different airplanes (ie, Boeing vs Airbus) that they just added to their fleet?

As an example, Delta has purchased many new Airbus A220. Since it is a new airplane and no one has any experience with it, do the pilots train the same for this new airplane and then based on their seniority one becomes Captain and the other a FO...or...they train for their respective position from the start?

Qualification for being a pilot-in-command in mutli-crew aircraft (i.e. captain) is independent of type rating (i.e. qualification to fly specific aircraft type). And similarly with the multi-crew rating required to fly a multi-crew aircraft at all (i.e. as F/O).

Therefore the airline selects some pilots and sends them to appropriate training to get the type rating. And those who were captains before can be captains on the new type too.

Since much of the experience applies to any aircraft, usually they'll select the more experienced captains from other types to become captains on the new type.

If the type is widely used elsewhere, the airline will also try to hire pilots from elsewhere who already have appropriate ratings, but obviously there is not much opportunity for that in a new type like A220 (formerly known as CSeries).


What was wrong with my answers to how to deal with low volt annunciator, and icing, both in IMC/IFR? I have questions for emergency situation in IMC.

I was asked about low volt or icing condition IMC from my school's checker.

The checker said "if you see low volt annunciator on PFD how can you deal with this problem under IFR flight?" So I answered "first contact ATC, and request radar vector to nearest airport and then, I will follow the check list for low volt annunciator." However, the checker said this answer was wrong.

Also, I got a similar question from the checker which is icing condition during IFR flight.  "When you face on icing condition under IFR flight, how can you deal with this situation?" So I also answered "first, I will turn on pitot heat, deforster and cabin heat, After that, I will do climb or descent to get warm air to rid of icing and try to get VMC condition. However, I will consider the altitude which is be higher than MEA. Also, I will do follow the check list for icing. If the problem is not solved, I will let ATC my problem, and request radar vector to nearest airport." But, the checker thought this answer was wrong too.

Is there any problem from my answers? Or could you let me know how I can deal with this low volt or icing situation in IMC?

Thank you very much!

Based on a 172S G1000

I wouldn't say your answer for the first question is wrong, but your steps are out of order. Before contacting ATC you need to verify the issue via whatever the POH says. On a 172S that means you will cycle the alternator switch and verify low voltage on the G1000 and whether or not the battery is charging. Do realize that the G1000s have a backup battery that provides x amount of backup time and it should have already been tested in the pre-flight and set to arm, if you verify the issue then limiting battery load and  contacting ATC would be the next step, never the first, and the value of backup time should be known and planned around(can't recall at this time, sorry).
I think this question is more semantics and specifics, he/she may not have liked climbing or descending as your only answer really, getting out of icing is the most important thing whatever the direction is, but I agree in general with climb/descent based on information. Asking for an altitude change I assume is implied when you say climb or descend. What you describe here is pretty text-book as far as dealing with icing to my knowledge.


Can I use my non-WAAS GPS receiver with ADS-B in the United States? I have a older style Garmin 530.  Can I use this GPS as the position source for an ADS-B installation?

In the USA, ADS-B requires a WAAS position source. A Garmin 530W can be used, but not a 530.

Here's a full list of FAA certified equipment needed for ADS-B. I hope that helps.


What is the differance between gliding for maximum range and gliding for maximum endurance? Is there a difference between gliding for maximum range vs. endurance?

Is the glide speed the same for max. endurance and max. range?

No they are different.

Gliding for endurance, maximum time in the air, is at minimum sink rate, which is usually close to stall because it's where maximum lift is being generated. In a glider this is the speed you thermal at.  In a power plane it might be the speed you'd glide at if you wanted to delay the inevitable as long as possible for some reason, say if your engine quit while sightseeing over a lava field during a volcanic eruption.

Gliding for range, flattest glide, is at max L/D speed for the weight, which also affected by the wind's effect on "effective" L/D or glide angle relative to ground covered.   If you were in the volcanic eruption scenario, it's the speed you'd wished you'd flown at as you realize you could have cleared the lava field if you'd sped up to best glide angle.

I'm only partly kidding around; inexperienced glider pilots can fall into a trap, when they get in sinking air, of slowing to min sink to minimize their rate of descent, when the proper action is to speed up to best L/D, or faster, to get through the sinking air as fast as possible, even though their sink rate goes up even more.  I tell students to think of sink as a rain shower while strolling; you run to spend as little time in the rain as possible.


What makes the Antonov An-2 have no stall speed? The Antonov An-2 is notable for being able to fly at a very low speed. However, what confuses me is that it has no stall speed:

  The An-2 has no stall speed, a fact which is quoted in the operating handbook. A note from the pilot's handbook reads: "If the engine quits in instrument conditions or at night, the pilot should pull the control column full aft and keep the wings level. The leading-edge slats will snap out at about 64 km/h (40 mph) and when the airplane slows to a forward speed of about 40 km/h (25 mph), the airplane will sink at about a parachute descent rate until the aircraft hits the ground."

(From Wikipedia article on An-2)

How is this possible? What makes the airplane have no stall speed?

The horizontal tail can't make sufficient down force to slow the plane to get the slatted wings to stalling AOA.  With the slat system, the stalling AOA will be perhaps 10 degrees higher than without.  With the AN2's large wing area, to get the slatted wings to stalling AOA might require the speed to drop to, say, 20 kt.  But the tail simply runs out of down-push before that angle is reached, in this case at 25 kt, so no stall can occur and the airplane settles into a near vertical mush as long as you hold the full up elevator.

Because there is no actual stall break or departure, the published "stall speed" is the lowest speed that airplane can be flown and maintain altitude.

Note that a "parachute descent rate" is about 20-25 fps, or 1200-1500 fpm.  That's still coming down pretty fast (you would probably collapse the gear landing normally at that descent rate) and the airplane will be wrecked when it hits the ground, but you'll live.

The interesting thing is that if you do get a slatted wing to actually stall, the departure can be very violent.  An acquaintance who flew a Pegazair he built, which has automatic slats, was horsing it around and was able to get an aerodynamic stall by using large elevator pulsations as he was approaching minimum speed, reported that it flipped over violently and his flight bag flew from the baggage well behind him up to around the windshield.  It recovered fine however.


Where must the glider tow line connection be? I have styrofoam glider and I want to pull it with a rope, to fly with me when driving a bike. Where do I need to connect the attachment point, if I want the glider to fly stable above me?
I think, to stop roll disturbance I need connect the rope at both wings, but where do I need place them, at the center of gravity (CG), at the center of the overall lift, at 1/4 wing chord (center of wing pressure), or at the aerodynamic center?

(I also notice that a plane tow real glider connects at the nose and when the winch tow connect at fuselage under wing, but what does this place represent in an aerodynamic sense?)

It needs to go just under the tip of the nose to have any chance.  This connection is equivalent to the thrust line of an engine, except that because the connection isn't rigid, the longitudinal location matters; the farther forward, the more stable (if the attachment is rigid, like an engine/propeller, it doesn't matter whether the thrusting component is forward or aft, from a stability perspective).
Probably most normal gliders hook up at the nose but a lot of them have hooks near the center of gravity underneath to facilitate winch launching, and when used for aerotow these are less stable and somewhat of a handful to fly for an inexperienced pilot, especially on crosswind takeoffs.
You will have to set the horizontal tail to apply enough trimming force to overpower the nose down component of the pull of the tow line, that is, more nose-up trim than necessary for free flight.
You will find that because the thrust line is more or less concentric with the roll axis, there is not much you can do for roll stability and will be stuck with whatever inherent stability is there from the dihedral effect of the turned up wingtips. Connecting the tow line to each wing tip will not help with roll, since the two lines still run to a single attachment (until you get the angle of the tow line to the longitudinal axis high enough that the "Y" connection is influencing roll, but the thing may still just arc down into the ground anyway), and connecting that far aft will make you completely dependent on the glider's inherent pitch stability and damping.
My prediction is that as is, whether you hook it at the nose or the wing tips, it will go all over the place, than crash, and to get it to just kite along smoothly behind while on tow, you will need a lot of wing dihedral, similar to a 2-control model.


For CG calculations, where is the root chord located on a swept wing aircraft? With a swept wing aircraft (specifically a MiG-25 I am modelling) where is the root chord taken from to calculate the location of CG?
Is it the root chord of the wing (where it attaches to the fuselage) or a projected line extended from the the leading / trailing edge to the centreline of the fuselage?

It's expressed in Mean Aerodynamic Cord. On a swept back wing, you can construct it as follows.


Why does the NASA GL-10 Greased Lightning run on diesel? I've been reading about NASA's experimental GL-10 Greased Lightning tilt-wing aircraft with interest.

My understanding is that this is a diesel-electric hybrid aircraft uses stored electrical energy to satisfy the much greater need for thrust during takeoff (and landing?), but for regular flying runs off fewer propellers powered by the 2x 8hp diesel engines (which presumably also are recharging the Li-Ion batteries for the next takeoff/landing) to achieve better efficiency.

The answers to this question show that diesel engines are generally poorly suited to aero applications, generally due to weight and complexity.

Why then does the GL-10 use diesel fuel instead of more common aero fuels?

There is a bit of a misnomer here, although the plane runs diesel engines it most likely does not run traditional diesel fuel as you would find at a gas station. Diesel engines can be run on Jet-A which is available far more widely than 100LL at airports outside the US which Ron mentions.

There are even some applications for diesel engines in GA as noted in your linked question the diamond twin star and now the Piper Archer DX have successfully been running diesel engines for some time now.

According to this paper the Cosworth AG engine was considered which the Navy has already been bench testing with JP-5 and JP-8 jet fuel. Presumably the GS motor they chose runs similarly.


Was my latest Air Berlin flight in violation of some in-flight procedures? I was quite surprised about one (all?) of doors on my latest Air Berlin flight. In particular:

the "Door locking indicator" was empty (black),
the "Cabin pressurized" light was not lighten and
the "Remove before flight" red strip was not removed.

(I am the owner of this picture and I authorize anyone to use it for any purpose except illegal activity.)

The plane landed safely and there was no noticeable in-flight change of air flow/pressure etc. Still, I wonder if the described situation is a violation of some in-flight procedures or at least odd in any way?

The safety pin is in its stowage position - ie. where it is supposed to be stored when not in use, as you can see in this video. The red streamer is usually tucked away out of sight, but some airlines seem to leave it visible. Also, it appears from your photo that the arming handle is over to the right, ie. in the 'armed' position, as it should be in flight.

The Door Locking Indication is green-lettering-on-black for LOCKED, as you can see at 0:28 in this video, or red-lettering-on-black for UNLOCKED. But that lettering may not be very evident unless you are quite close to the door and looking almost directly at the indicator.

As far as I am aware, the Cabin Pressurized light is not normally illuminated in flight - it flashes red if-and-only-if the door handle is moved towards the OPEN position AND the cabin is pressurized, as you can see at 1:04 in this video.


How to secure an aircraft at a transient parking space? I've noticed that at many airports, the transient GA parking spaces often don't have tie-down anchors (e.g. bolts drilled into the pavement; heavy steel cables, etc.) or tie-down ropes. They simply have a "T" painted on the ground to indicate the parking alignment. This is true even for many FBO-managed parking spaces.

How should I secure my airplane at these parking spaces? Even if I had my own tie-down ropes, there's nothing to attach the ropes to.

I'm hesitant to just chock the wheels, as this does not prevent a gust of wind from blowing the aircraft around.

Should I ask if there's a patch of grass and use an artificial temporary anchor/Klaw system? Is this even commonly available at your average GA airport?

Note: I only need to park the plane for a few hours, not overnight.

Tie downs are generally for overnight or longer.   Nobody ties down an airplane for a visit of a few hours unless there is something forecast in that few hours like high winds or thunderstorms.  And if that's the case, you will want move it somewhere on the airport that has unused permanent tie downs or inside a hangar for the duration of the weather event.

Most screw or spike-in grass anchor systems are useless for serious winds and are easily pulled out.  There are several Youtube videos that demonstrate how ineffective they are, with the exception of one system that uses large spade like blades driven into the ground.


How to interpret the published altitudes for each of US STAR procedures? I have been studying the STAR procedures, as published by FAA, and I am trying to understand the way that the altitudes are defined for each fix/route. Take, for example, CAMRN4 of JFK.

I see the MEA (Minimum En-route Altitude) of the segment from SEA ISLE to BOTON. Then, no altitude restrictions are applied except when reaching HOGGS, where there is an expected altitude of FL180. The next waypoint with a defined expected altitude is CAMRN, with an expected altitude of 11000ft.

What happens in the intermediate segments (HOGGS --> PANZE --> KARRS...) in terms of altitude? When along a controlled arrival, for example in this specific STAR (CAMRN4), how is the altitude controlled between waypoints when nothing is explicitly stated on the procedure diagram?

The main reason I am asking is because I have been trying to understand Arrival/Departure Procedures and I see that altitude information is often sparse or even completely lacking from some of the diagrams.

Some STAR procedures provide altitude limits on them, so ATC would say:

  Descend via the X arrival

All of the needed restrictions are published on the chart. Since the CAMRN4 does not provide hard limits (just "expect" altitudes), ATC will provide pilots with altitude restrictions per other traffic and their SOP, such as:

  Cross HOGGS at FL180

For most arrival procedures, it wouldn't be critical to restrict altitude at every fix along the route. Any important restrictions would be included. If a fix doesn't list altitude restrictions, then no special restrictions apply. It's up to ATC to provide additional restrictions as required. Once an aircraft gets to the approach phase, altitude becomes more critical, and there will be more restrictions noted.

If you imagine a flight path through space, only two points are required to define a line. You could even consider the top of descent as one of the points, determined by the aircraft's rate of descent. Altitudes at the other points can be determined by that path. A modern Flight Management Computer is able to provide Vertical Navigation guidance, so that an airplane will basically follow that path to cross fixes at the required altitudes. Without this system, pilots would be expected to either manually adjust rate of descent to follow the restrictions, to perform an idle descent to the next restriction. On the CAMRN4, it would be fine by the chart to dive to 11000 after HOGGS, but this would not be expected or efficient. Some arrival procedures may be steeper or shallower than an open descent.

Note that the CAMRN4 says it is applicable to turbojet aircraft only, and pilots should expect FL180 at HOGGS and 11000 at CAMRN.  Pretty much any aircraft on this STAR will be well above that 6000 MEA. If they do happen to be that low, the MEA should keep them clear of the Atlantic City class C that extends up to 4100 ft. Other than that the general minimum altitudes in the area would apply.


How did flight 2574 break up? My understanding of Continental Express flight 2574 is that a de-icing boot on the horizontal stabilizer of the EMB120 was missing screws and therefore detached, leading to the tail separating.

I would appreciate an explanation, with as much aerodynamic information as necessary, for how the tail separation could be caused by the boot removal.

It didn't directly lead to the tail separating. What separated wasn't just the de-ice boot, it was the whole leading edge on the left stabilizer. That caused a stall of the left horizontal stabilizer and an increase in drag on the left side. The wings of an aircraft have a tendency to pitch the aircraft down (as they're behind the center of gravity and provide a force upwards), while the stabilizer produces a force downwards to keep the plane's pitch stable. With the loss of lift on the left stabilizer, there was less downforce (leading to a pitch down), more downforce on the right than on the left (leading to a right roll), and more drag on the left than the right (leading to left yaw).

These rather violent motions led to massive aerodynamic loads on the plane, resulting in the next failure: the left wing. When this failed, the plane violently rolled right, for reasons I'm not quite sure of (I get violently rolling, but am unsure why it was to the right). This roll stressed the plane even more, and that is when the tail ripped off the plane. The direct cause was extreme aerodynamic forces caused by the flight path, not the leading edge separation itself.


Why does weather radar not report some precipitation? Not sure this is the right place for this, but how come I look at the radar sometimes and, despite it clearly raining at my present location, it doesn't show any precipitation? Example is right now at KEWR, it's raining. I can verify that by standing outside. But looking at the radar from several sources (NOAA, weather.com, several iPhone apps) there is nothing on it.

I know about the whole tilt thing but KEWR has a terminal radar quite close as I recall most airports do.

The National Weather Service's 148 WSR-88D Doppler radars can detect most precipitation within approximately 90 mi of the radar, and intense rain or snow within approximately 155 mi. However, light rain, light snow, or drizzle from shallow cloud weather systems are not necessarily detected.—wunderground

As Ron Beyer commented, the METAR KEWR 010251Z 03012KT 5SM -DZ BR BKN007 OVC012 14/13 A3025 RMK AO2 SLP243 P0000 60002 T01390133 58001 shows light drizzle.


Can I listen to control tower frequencies on a ham radio legally Is there a frequency I can tune into to listen to airport I’m in Durham by RDU AIRPORT and would like to listen in on a ham radio only legally

In North America, just buy an air-band radio and listen to Raleigh-Durham tower all you like, or if your ham unit receives the aviation VHF frequencies, do that.  Or find it on LiveATC.net  It's only illegal to broadcast without authorization, not listen in.


How can an helicopter end up with the same tail number than an airplane? For example, take N133AA.

https://www.jetphotos.com/registration/N133AA shows American Airlines photos from the 90s and an helicopter from this decade:

The FAA only shows the helicopter registry:

https://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=N133AA

Transtats shows that the last time N133AA flew from LA to NY was in 2008, and I'd bet that was not the helicopter.

Is it normal that tail numbers get reused? How can I make my cross-searches reliable?

N133AA appeared on an American Airlines DC10, but American Airlines retired, sold or scrapped all their DC10 and MD11 aircraft by 2002, releasing the registrations for other uses.

Wind the clock forward 15 years and somebody has used N133AA for a Robinson R44 helicopter. I speculate that the effective owner of the helicopter is one Agustin Anaya, who submitted the photographs to JetPhotos, even though the aircraft is registered to a company.

The FAA registry shows only the helicopter because the American Airlines usage was released long ago.


What are the weights of vertical and horizontal stabilisers of a Boeing 747-400? For my math exploration (IB) I am doing something related to aircraft. So I was wondering what the weights of the horizontal and vertical stabilisers were. If you do know the weights please state the source of the information too.

From my time as an intern at the plant at Paine Field, I know that a 747-400 wing and center fuselage section weighs 42 tons.  That's just the structure itself.