How are evacuation tests made as realistic as possible? I've seen the video of the A380 evacuation test and similar ones.

While the fast evacuation is impressive, a criticism often heard (and read in the comments on YouTube) is that these people were prepared and (roughly) knew what was about to happen. Also, people in the back of the queue were not in fear of their lives, so they just waited on their turn.
No one tried to go against the stream to look for loved ones seated in different rows, no one tried to get at their personal belongings to try and take those with them.

What measures are taken to make evacuations tests as realistic as possible?

I've heard that incentives are offered to passengers to get out as fast as possible, for instance $100 for the first X passengers to get out. Is that true? If not, anything else?
I of course appreciate the conflicting interests that while ideally the test should be as realistic as possible, the test passengers can't be endangered.

The only ‘realistic’ way of carrying out a full scale evacuation of an aircraft would be to put people in it and set it on fire. That said, FAA takes some efforts to keep the evacuation tests as realistic as possible without seriously endangering the safety of the 'passengers'. The FAA Advisory Circular 25.803-1A - Emergency Evacuation Demonstrations lays out some rules regarding this.

Only half the exits are used for evacuation by a representative mix of passengers, with some debris (luggage, pillows etc) strewn in the path.
The aircraft is to have the maximum number of passengers and flight crew, with a representative mix of age and genders with dolls for children.
Not training any of the participants in the test, i.e. both the flight crew and the participants are not trained to evacuate the (that particular) aircraft. According to the Advisory Circular,

  The flight attendants should not be trained for specific demonstration conditions, except that specific training should be given which relates to the safety of the participants prior to and during the demonstration.

The participants are clearly told what they are going to do.

  The prospective participants should be informed of the purpose of the demonstration and the expected duration of their participation.

Though the participants know 'why' they are there, they are not supposed to know 'when' demonstration is going to start.

  Neither the crew nor passengers should hear or otherwise receive any indication that the demonstration is about to begin. The first indication to participants should be the extinguishing of the normal cabin lighting.

The participants should not know about the evacuation plan beforehand.

  If safety devices or any other equipment external to the airplane could indicate to the test participants which exits are to be used in the demonstration, passengers and crew should enter the airplane through a tunnel or other means that will prevent them from seeing that indication.

The participants are more than likely paid (employees with previous knowledge of the system are not allowed), though there is no mention of any 'prize' for first getting out. The regulations simply state,

  Prospective participants should be informed of any direct benefits to them (e.g., pay, meals, etc.) and of benefits to society

The participants are prevented from interacting with outside and to recieve any information from outside the aircraft.

  ...exterior windows should be obscured from the outside to prevent both viewing of the outside conditions and any ground lighting from shining into the airplane.

There is intense debate over how 'realistic' the evacuation tests are. For example, the evacuation of British Airtours Flight 28M, a Boeing 737 took more than 5 minutes (resulting in the deaths of more than 50 people), though the aircraft had passed the test.

According to Aircraft Evacuation Testing: Research and Technology Issues, there are multiple problems with this type of testing:

There is only one data point (Full scale evacuation tests are costly; each one costs nearly $1m)
The conditions do not reflect the actual ones experienced (for example, fire, smoke etc.)
The participants know why they are there (Employees of the manufacturer are not barred, though they may not sit near the exits).
The participants do not reflect the actual demographics of the flying public, and if considered, increased the evacuation time significantly (obviously, disabled people and kids are not there in demonstration).
The participants do not experience any trauma. Of course adding smoke or fire is not an option as already around 4-5 percent people are getting hurt.

Image from Aircraft Evacuation Testing: Research and Technology Issues
September 1993 OTA-BP-SET-121 NTIS order #PB94-107620

As a result of the aforementioned BA28M accident, UK's, Cranfield Institute of Technology (CIT) carried out a number of tests which included a case where financial incentives were offered to foster competitive behavior among
test participants. The study determined that,

  the presence of a competitive element had a significant impact on egress
  rates for evacuations through the bulkheads, but did not affect the rate of evacuation through the Type III exit

Note: According to FAA, This type is a rectangular opening of not less than 20 inches wide by 36 inches high, with corner radii not greater than one-third the width of the exit, and with a step-up inside the airplane of not more than 20 inches. If the exit is located over the wing, the step-down outside the airplane may not exceed 27 inches.

The US Department of Transportation also carried out studies, which resulted in similar conclusions.

Image from Aircraft Evacuations Onto Escape Slides and Platforms I: Effects of Passenger Motivation, DOT/FAAAM-96/18

The study found that the introduction of smoke did not have much effect, but noted,

  Although this research design biased against revealing any deleterious effects of smoke on egress, previous studies using smoke had shown robust reductions in egress speed.

Giving monetary incentives to participants reduced the time required for egress.

Image from Aircraft Evacuations Onto Escape Slides and Platforms I: Effects of Passenger Motivation, DOT/FAAAM-96/18

In this study, the 'competitive' group were offered a financial bonus of $50 to be among the first 25% passengers to evacuate the arcraft. However, the passengers in the competitve trials

  ...(became) more aggressive and climbing over seats, outmaneuvering other passengers, etc. to get out quickly.

resulting in broken over seat backs, among others. I suspect participant safety is the main reason FAA doesn't offer any incentives duing demonstration.

Because of these reasons, simulations are being increasingly used in modelling evacuations which include variables like crowd behavior, state (of the person), mobility, etc.


What high-lift devices are used on the Bombardier Dash 8 Q400? What type of flaps, slats or other high-lift devices are used on this aircraft?

The Dash8 - Q400 - Aeroplane General PDF (courtesy of smartcockpit.com) indicates on page 27 that there are inboard and outboard flaps.

Reading through the Dash8 - Q400 Flight Controls PDF (also from smartcockpit.com) indicates that:

  Two single-slotted inboard and outboard fowler flaps are attached to the trailling edge of each wing (Figure 12.8-1).page 43

There is no indication of slats or any other high-lift device.


What is the process of obtaining a commercial license after revocation? I held a 2nd class medical and a commercial pilot license. My certificates were revoked due to an alleged DUI which I didn't get convicted of. I have been trying to contact every division in the FAA just to speak with someone about the process of getting my certificates back, however, due to COVID-19 not a soul is in the office nor, apparently, returning phone calls. Any ideas on which direction to go to obtain my certificates? Or possibly a direct number to someone to speak with about the matter?

If your pilot's certificate was definitely revoked then it's gone for good. You'll have to reapply and re-qualify for all your certificates and ratings again, although you have to wait a year first per 14 CFR 61.13(d)(2):

Unless otherwise authorized by the Administrator, a person whose
pilot, flight instructor, or ground instructor certificate has been
revoked may not apply for any certificate, rating, or authorization
for 1 year after the date of revocation.

Certificate revocation is the FAA's 'nuclear option' and they don't do it lightly. Your best option here is to contact AOPA (if you're a member) and/or an aviation lawyer for specific advice.


What is (theoretically) the most efficient shape for an aircraft, assuming you don't have to carry any cargo? Assuming that you don't need to have any large piece on the underside dedicated to storage area/people (as all planes do) and you don't care about stability, what is the most energy efficient form for an aircraft in terms of energy required to maintain altitude? I would guess that it is the flying wing.

What it should do:

Use computer control if needed to reduce power requirements

All other requirements take second place; efficiency is the dominant goal.

The best shape for an airplane or glider would look like the ASH-30mi, an open class glider with an 86.9ft wingspan, and a 41:1 aspect ratio (wing length to wing chord). It has a glide ratio exceeding 60:1, and is considered the state of the art for gliders.


FAA Aircraft Registration Form AC 8050-3 doesn't exist I am preparing to certify a self-built aircraft as flightworthy and legal to fly, and was reading the required documents listed on FAA's Amateur-Built Aircraft Airworthiness Certification page when I realized that FAA does not have the required document "AC Form 8050-3" when searching the form on the FAA Forms website. Is this some kind of mistake? Or is the form possibly a form located inside of a larger form, which could explain why it isn't showing up (Because if that were the case, it wouldn't be its own individual file)? If anyone could provide a link to this form, that would be great.

That's because 8050-1 is the Aircraft Registration Application, and 8050-3 is the Certificate of Aircraft Registration.
You submit 8050-1, and the FAA sends you 8050-3.


What are the negative associations with Continuous Descent Approach? According to this Wikipedia article:

  Due to the negative association with the term CDA,[citation needed]
  new procedures introduced at LAX and other US airports are instead
  called optimized profile descent (OPD).

What are the negative associations with the term CDA?

From ourairspace.org*:

The FAA wanted to implement Continuous Descent Approach (CDA) at La Guardia as part of the Regional Airspace Redesign to reduce the noise impact when they terminalized a much larger area. In the Draft Environmental Impact Study (DEIS) CDA was included however CDA failed the safety field test in the summer of 2007 and was not included in the Final Impact Study (FEIS).
(...)
The FAA decided to rebrand CDA due to the safety and noise risks discovered overseas and in litigation so they changed the name of the procedure from “Continuous Descent Approach” to “Optimized Profile Descent” (OPD).

Note it says, "... was not included in the Final Impact Study," which to my understanding means the specifics did not make it to the final report (I tried to look for that report, others may have better luck).
They mention failing a safety test, and similar overseas issues. From this paper (atmseminar.org), the one thing that stands out is the need for 4D (time based) traffic management to make it work in high density areas.

This paper has shown that the conflict-free continuous descent approach flown in high density traffic can be achieved based on the 4-D trajectory concept. The proposed scheduling algorithm is proved to be effective in strategically solving the conflicts occurring in the inbound traffic in a full day simulation of terminal airspace operations.

Which means relying only on what each FMS wants is not enough. The ATM systems need to account for all the airborne FMS's, and based on that delays can be introduced for proper management. Not an easy feat.
For comparison, in Europe the CDA and CCD in high density traffic still does not have an IOC (Initial Operational Capability) date. One of the building blocks is expected in 2023.

* [A] volunteer organization of professionals who are committed to addressing and reducing aviation noise and emissions while supporting a safe robust aviation industry.


How do insurers apportion responsibility when airliners collide on runways or taxiways? Here's an ATC recording of Virgin and Egyptair aircraft clipping wings at JFK.

Generally, what happens next with regard to sorting out responsibility after a low-speed collision that results in damage to commercially-operated aircraft? (I'm talking about a return-to-gate type of collision where passengers are inconvenienced, rather than a serious evacuation-style incident.) There seems to me lots of factors, for instance:

The captains are in charge of their aircraft, but what if ground controllers gave them poor instructions?
When a parked aircraft were damaged by a moving one, the former might seem the innocent party, but what if it were stopped in the wrong place?
It's possible that an airport itself might have listed incorrect information about its taxiways that leads to a collision.

In automobile accidents, its the insurers who would sit down and come to some agreement, but there's not really an equivalent of the airport in such circumstances. And the stakes are quite high - repairs and delays might be very costly to an airline.

I presume there's always some sort of regulatory investigation, but their prime concern I would think is to stop it happening again, which is not the same as agreeing responsibility and liability. The question is: how do insurers decide who ends up paying, for what is almost always a very expensive error?

 source

Insurance is a contract between the airline and the insurance company. Typically, the airline is simply compensated an amount by the insurance company and the case is closed.

Demand to another party for settling damages only occur if the damages is unusually large and one party is mostly at fault. You have to consider the time and cost taken into legal proceedings as well.

Insurance compensation actually occur more frequently than you think. For example, at my airline, someone either forgot to apply the brakes on the food trolley or the brakes failed. Either way the trolley smashed into something during ground operations, resulting in damage to the trolley itself (I heard it was destroyed). Insurance paid us.

Regarding the specific incident about airplane collisions on taxiways, it is highly unusual. My guess would be it was handled as a "special case" in this instance.

You are correct that any investigations, if any, focus on preventing future occurrences rather than assigning blame. Settling damages is a civil matter; as such insurance companies rarely launch their own "investigations". Even if they do, it would just be a corporate and expensive version of two drivers using dash cams to argue who has to pay for the stretched bumper.

At any rate, insurance may compensate the airline even if employees of the airline are at fault. That is what insurance is for.


How does the 3 pin ground power connector (AN2551) work? I understand the premise of the 3rd (smaller) pin (top of the image) is to delay switching power until the two main pins have made positive contact with the aircraft socket on plug insertion; and similarly, to disconnect power before the two main pins lose contact on plug removal.

This setup is desirable as it;

ensures correct polarity as the plug only fits into the socket one way
avoids arcing on insertion and removal which in turn;

removes a potential source of ignition (especially if refuelling)
prevents damage to the socket and pins

My understanding is that all pins on the plug are always live and that all control logic and switching is part of the aircraft's electrical system. ie: the switching occurs internal to the aircraft between the ground power socket and the main bus via a relay (powered by the external power source) that is ambiguously referred to as the external power relay (referring to its function, not its location).

I have several questions;

If the plug pins are always live, why does the third pin not present a potential arcing risk? (I assume the lower power has something to do with this but you can get a reasonable spark from a 9V battery).
How is the power on the 3rd pin limited?
Why not use the 3rd pin to switch the power at the source so that the positive pin is only ever live when connected?
eg: short the 3rd pin to the ground pin on the aircraft socket to activate an external relay (part of the power supply - not to be confused with the relay in the aircraft referred to as the external power relay) to switch the power on/off before it even reaches the aircraft. As a bonus this would also  (slightly) simplify the aircraft electrical system.
Is all the control logic always in the aircraft?
Is any aircraft power required? ie: will this work if the aircraft battery is completely dead?
Is the aircraft battery required to be physically connected (to complete the circuit for the relay)?

Sources that got me this far:

https://www.askmehelpdesk.com/aviation/3-pin-ground-power-unit-connector-aircraft-375477.html
http://aircraftplugs.com/download/i/mark_dl/u/4008094775/4627385351/purpose_of_third_positive_terminal.pdf
https://www.industrial-electronics.com/images/aircraft_8-9.jpg

The key to how it works is best explained with the 3rd link in OP question: the short pin provides power for a relay switch, powered = closed. When pulling the plug out the short pin disconnects first, opening the switch which removes power from the plus (middle) terminal of the plug before it is disconnected from the counter-plug.


Rules and restriction for toy UAV in India on very low heights ? (max 50 meter from ground ) We want use RC UAV to take some pictures of  heritage forts (Gadh) around Pune. Do I need a special permission for that ? I have seen some one doing it before but just for to be sure I need to know. is there any official government website that can guide us ? I am so concerned because I want to do a research project.

A public notice issued by the DGCA in October reads: “DGCA is in the process of formulating the regulations [and globally harmonise those] for certification & operation for use of Unmanned aircraft systems [UAS] in the Indian Civil Airspace. Till such regulations are issued, no non-government agency, organisation, or an individual will launch a UAS in Indian Civil Airspace for any purpose whatsoever.”

...

  “There are no regulatory guidelines concerning the sales and operation of such aircraft. So when a request is made for the use of drones we allow it on a ‘case-by-case’ basis. If we feel that they would not pose any security threat or cause any traffic snarls, we allow the request,” explained another senior police officer.

The Hindu, December 24 2014


Is there absolutely any way (hook or crook) to listen to ATC in India, especially Bangalore? We can listen to various ATC radios across the world, but I really want to listen to the ATC at VOBL.

In principle you can listen to ATC of VOBL (Kempegowda International Airport, Bangalore) using a VHF air band radio receiver on the following frequencies:

Tower: 124.35 MHz
Ground: 121.65 MHz
Approach: 121.25 and 127.75 MHz

It is however illegal to own such a receiver in India:

  Prohibition of possession of wireless telegraphy apparatus
  without licence.—Save as provided by section 4, no person shall
  possess wireless telegraphy apparatus except under and in accordance
  with a license issued under this Act.

(The Indian Wireless Telegraphy Act, 1933, emphasis mine)

There used to be coverage of Mumbai ATC on liveATC.net, but according to this thread on pprune.org it was shut down, presumably because it is illegal to pass on ATC transmissions in India.

See also:

Is it illegal for Joe Public to listen to ATC in the UK?


What's the smallest 3-blade propeller for this motor? I've got a 15470 brushless 35kw motor from China
How do I find the smallest 3-blade propeller I can use for this motor?

Here are it's specs,
Max Power: 35KW
Max Amp: 400A
Max RPM: 8500
Max Volt: 120v
Torque: 75Nm
Resistance: .94

I've looked into eCalc but it's for determining power / thrust, etc and not finding prop size.
Any help would be appreciated!

You need the largest prop that keeps the tip speed below about .9 Mach, roughly 1000 ft/sec, so you want the largest propeller than can operate at that RPM at .9 mach.  Here's a tip speed calculator for larger propellers that should suffice.


How safe is IFR in class E? In class D and E airspace, there is no separation between IFR and VFR traffic. However, most airspace in the United States below 18,500 feet MSL is class E airspace, which is exactly where non-pressurized aircraft cruise when flying IFR.

My question is not about regulation (that's perfectly clear: no separation between IFR/VFR) but I'm curious to learn how safe it actually is when cruising at 10,000 feet in VMC on an IFR flight plan while in class E airspace. I'm pretty sure many pilots will be on autopilot without taking too much notice of what's happening outside but according to the regulations the pilot is still responsible for seeing and avoiding other VFR traffic.

Are there any accident statistics on this? I have read hundreds of accident reports over the last few years and I can't remember ever seeing a report on a midair collision between IFR and VFR aircraft in class E.

As with any flight, "It's as safe as you make it".

The vast majority of the General Aviation fleet (piston singles) don't even have an autopilot, and the ones that do may only be single-axis units (wing levelers), so the pilot has to have some level of attention on flying the airplane.
If we assume these are the folks flying around VFR we can also generally assume they should be looking out the window the vast majority of the time (like Skip said, "Put down your iPads and do your job.")

Adding to that, "See and avoid" is every pilot's responsibility in VMC - whether operating under Visual Flight Rules or Instrument Flight Rules - if you can see, you are expected to avoid (and if necessary deal with ATC freaking out about you deviating from a clearance later).

A number of other steps have been taken to enhance safety in Class D and E airspace:

In the US FAR 91.159 prescribes specific VFR cruising altitudes, and FAR 91.179 is the IFR equivalent.
The cruising altitudes in these regulations result in an automatic 500-foot vertical separation of VFR and IFR traffic (at least between 3,000 feet MSL and 18,000 feet MSL - which is where VFR and IFR traffic are likely to be mixing in cruise. ).

Additionally IFR traffic is usually receiving radar separation services (there are some non-radar areas in the US, but not many). Nominally this separation is "IFR-to-IFR" in Class E airspace, but if a controller sees a VFR target squawking 1200 and behaving unpredictably they can vector IFR traffic around it.
Similarly if a controller sees a "primary target only" (something without a transponder, and not reporting altitude information) they will often vector IFR traffic around it until they can establish what it is and what it's doing.

Within class D airspace the level of service you'll get depends somewhat on the equipment the controllers have.  A "purely visual" tower with no radar can only give traffic advisories for aircraft they can see by looking out their window, but if they see a conflict they're going to say something. A tower with radar (either local or slaved from a nearby airport) may give VFR-to-VFR or VFR-to-IFR separation advisories based on that data as well, sometimes including advisories to aircraft inbound who are outside their airspace.


What are the best methods for calculating lift during different stages of flight? Supposing I have the all dimensions of an RC airplane: wingspan, NACA airfoil, aspect ratio, fuselage length, etc., what would be the best methods of calculating the expected lift the aircraft should feel during takeoff, climb, and cruising stages? The conditions are assumed to be that of sea level.
I also have estimates of thrust produced by the propellers on the airplane, center of gravity location, stall speed and lift off speed

As we have learned here at Avation Stack Exchange through many writings: thrust or power variation is critical in take off, climb, and cruise flight.
In straight line steady state flight (at the same speed) lift only equals weight in level flight, in climb or descent it is equal to the cosine climb or descent angle x weight.  In a climb the engine must provide the remainder of vertical lift, in a descent drag reduces vertical lift requirement.
Plugging in some numbers for cosine, we see lift is close to weight until climb or descent angles exceed around 20 degrees. (Cosine 10 degrees = 0.98 Cosine 20 degrees = 0.94)
Lift may exceed weight during maneuvering, known as "G's".
This involves curving flight.  Every plane has a G limit, even models.  But in straight line flight, under most conditions, lift produced is fairly close to the weight of the plane, and is governed by airfoil type, wing area, air density, speed, and angle of attack.


What happens when you put vortex generators on both sides of a symmetrical vertical tail? What happens when you put vortex generators (VGs) on both sides of a symmetrical vertical tail?

I understand a horizontal tail with a classic foil like a NACA 0012 has a max cl of about 1.5.

I understand VGs add about 0.6cl.

What happens when you put VGs on both sides of the vertical tail?

For sure it will allow lower speed or better control at lower speeds, but will it actually bump the max cl from 1.5 to 2.1 at positive and negative angles of attack?

That's a 40 % increase in performance!!!

So.... can I decrease my vertical tail by roughly 40% and still get a similar EFFECTIVE vertical tail volume ( vertical tail moment)?

Just because VGs can delay the flow separation (with no guarantee of success), it doesn't mean you have increased your tail volume. In fact, you have the exact same tail volume unless your vertical tail is separating at small sideslip, which probably indicates bad design or bad manufacturing.

If the VGs do increase the max Cl, it means you may be able get to a higher slip angle, perhaps more crosswind capability if your rudder is up to the task.


Why is it appropriate to announce ‘stable’ on final approach? I have recently discovered that a budget airlines flight deck in the UK (Airbus 320) announce ‘Stable’ on the final approach. Both the Captain and F.O, just after 500 ft is called out by the computer.

It does seem obvious and yes, the word does speak for itself, but why does it need to be verbally announced?

Is it similar to the same reason when ‘Thrust set’ is announced? To acknowledge that they are happy with the appropriate aircraft instruments and performance, and that it is ‘stable’ and safe to land? I know ‘hundred above’ is a great way to warn the crew that minimum is coming very soon so does stable lead them into this ‘is the aircraft able to proceed’? If one was to not agree that it was ‘stable’, not quite sure what that means at this stage, it does not leave them much room for negotiation does it? Aside from the obvious, what could make one pilot disagree with ‘stable’?

The FAA offers some advice on this:

  An unstable approach is simply an approach that does not meet the
  criteria for a stable approach established by the aircraft operator.
  As an illustration, Flight Safety Foundation defines a stable approach
  in the following terms:

  On the correct flight path:

  ILS Approach - ILS within 1 dot of the localizer and glide slope.
  Visual Approach - Wings level at 500 feet AGL.
  Circling Approach - Wings level at 300 feet AGL.
  Only small heading and pitch changes required.
  Speed within +20/-0 kts of reference speed.
  Aircraft must be in proper landing configuration.
  Maximum sink rate of 1,000' per minute.
  Appropriate power settings applied.
  Briefing and checklists complete.
  During IMC - Stable by 1,000 feet AGL.
  During VMC - Stable by 500 feet AGL.

  If the approach is not stable by 1,000 feet AGL or 500 feet AGL
  (depending on weather conditions), or if the approach becomes unstable
  below these altitudes, the pilot should initiate a missed approach/go
  around. The pilot may initiate a go around at any time above or below
  these altitudes if deemed necessary. It is possible for a pilot to
  initiate a go around even after touchdown on the runway, but not after
  the thrust reversers have been deployed.

They are simply verbally verifying the approach is stable and they don't feel they need to go around. I would think Various OpSpecs dictate how go-arounds are initiated but in reality either pilot can initiate a go-around.  If an approach is unstable a go-around should be initiated.

IATA advises that callouts are used which may be why carriers are adopting them.

  Furthermore, the adoption of calls of “STABILIZED”, “UNSTABLE” or
  “GO-AROUND” at a given point on the approach (stabilization
  altitude/height for example) may improve decision making and
  compliance to ensure a timely go-around is carried out. While a
  “STABILIZED” callout might be required at either 1,000 feet or 500
  feet above touchdown, the “GO-AROUND” command can and must be made at
  any time prior to deployment of thrust reversers. Once again, if such
  callouts are adopted it is essential that an acknowledgement is made
  by the other pilot in every case


Does the Piper Aztec have flaps and slats and if so what kind? I was just wondering if any one knows if the piper Aztec has flaps and what kind. Also if the piper Aztec has any other high lift devices.

The Piper Aztec has standard (plain) flaps:

Source: Sky4Buy.com

Another View:

Source: Same as above

The Aztec does not have slats as can be seen in the image from the front of the wing:

Source: NWAviators.com

Here is a close-up view of the wing of the plane in the first two images (damaged, but no slats):

Source: Sky4Buy.com

Other than the flaps (and wings) there are no other high-lift devices installed on a Piper Aztec.


Is there a website which highlights airport locations on a map? Is there a good website which shows airports (both public and GA)? I can look it on Google and Bing Maps (as shown in the image below). Shown the picture, I have zoomed in a lot to see airport icons (bottom left and top right). I feel that the icon on Bing (right) can be easily spotted than the one on Google (left). Even if I zoom out one level, Bing still shows both airports but Google doesn't.

When I search on Internet, mostly A/F Directories are returned. Wikipedia also has a thorough list but I don't like plotting them on a map to find their proximity.

SkyVector is a great resource for aviation maps and data of all kinds. It offers worldwide sectional- and low-ifr-type charts, and a fully-featured Airports section.

I'm not sure if you also want airport diagrams, but you may also get some decent results with OpenStreetMap. The open source maps have some hit-or-miss levels of detail for airports, some including full taxiway and runway data. Others are just property outlines.


Why is there such a large price difference between the A350 and B787? What are the reasons for quite significant difference in price between the Airbus A350 and Boeing 787? List prices for the A350-900 and 787-9 are around 317 million USD and 190 million USD respectively.

Those prices are not the actual prices airlines pay for those planes. They get big discounts and more complex contractual terms. It's not like buying a box of pasta.
In conclusion, you can't assume that the price difference means a different cost of the components for the manufacturer


Where to find the various cargo hold dimensions and volumes of transport aircraft, such as the A330-300? What are the dimensions of the cargo hold on the Airbus A330-300? (In order to check the usable space for containers or baggage.)

I'm looking for the internal dimensions of the hold with its subsections in the Airbus A330-300, i.e. length, width and height. What are they? This is in order to understand how much space there is and and how it's divided for standard containers or for baggage in bulk configuration.
I'm looking the value of volumes of the parts of the hold, too.

The [relevant] dimensions of the cargo compartments are published by the manufacturers. For all Airbus planes, visit: Airbus / Airport and Maintenance Planning. You can also search for other manufacturers.

For the requested number of containers, here they are for the A330-300/900 (no need for the volume as the containers are standardized):

The documents also include the locations of cargo doors.


Would an aircraft with contra-rotating propellers longer than the plane's wingspan be able to fly? I enjoy taking the time to try and visualize how fictional aircraft might actually work in reality. Unfortunately there are some that seem highly impractical from an engineering student's point of view.

One in particular is the Bella Ciela from "The Place Promised in Our Early Days." It features a set of blade-like wings that protrude out front and deploy into contra-rotating propellers, sustaining flight after its jet-assisted takeoff. The blades spin much slower than a conventional propeller as well.

I can get by the closed-loop wing. The V-tail has no issues as far as I can see. My main concern is the large rotating blades that extend far beyond the wingspan of the plane. Taking the Bella Ciela's design out of the equation and focusing on concepts alone..

How feasible is it to use a propeller larger than the wingspan? Is there any law of physics that prevent this configuration?
What immediate consequences would be seen in the airflow behind such a large propeller? Would the wings aft of the flow still be able to produce stable lift?
The blades remain flat when stowed and act as an additional lifting surface; but I assume one could position them so that their loss of lift doesn't affect the balance of the plane (like in the sketch, with them centered)?
Without twist, can a propeller still provide efficient thrust? Could you reproduce the twist's effect by instead varying the length of the blade's chord from root to tip?
Are there standard equations for calculating thrust and drag of a propeller that does not have twist? Or of a propeller in general?

I can already see how drag would be a huge issue with spinning something so big. Is there a limit to how long propeller blades can get?

My apologies if I am asking [too many] questions that do not fit this board's criteria. This is just a concept that has had me Googling around for the past few hours. It's neat, and I hate dismissing things as just art without at least trying to justify them.

Short answer: This design will probably work, but it will not be very efficient. It can be tweaked into flying, but when you start tweaking, you would continue such that the outcome would look differently.

Now let's look at your questions one by one:

  How feasible is it to use a propellor larger than the wingspan? Is
  there any law of physics that prevent this configuration?

There is no law which forbids such a large propeller. In order to create thrust, you need to accelerate a mass of air backwards. The larger the propeller, the smaller the acceleration needs to be for a given thrust, since a higher mass flow is available. This makes large propellers inherently more efficient, but larger blades are heavier and also produce more friction drag, so the sweet spot is at propellers which are quite a bit smaller than the wings of the aircraft they are attached to.

  What immediate consequences would be seen in the airflow behind such a
  large propellor? Would the wings aft of the flow still be able to
  produce stable lift?

Since the acceleration provided by the propeller to the air mass is small, the wings behind them would fly in almost undisturbed air. The lift will wobble a little over time, because the boundary layer flowing off the propeller blades will produce a cyclic variation in dynamic pressure on the rear wings. This will, however, not impede their general capacity to create lift.

  The blades remain flat when stowed and act as an
  additional lifting surface; but I assume one could position them so
  that their loss of lift doesn't affect the balance of the plane? (Like
  the sketch with them centered)

At slow speed it helps to have more wing area for lift creation. Note how much the fowler flaps of an airliner move backwards to increase not only the wings camber, but also its area. Using two wings flying in formation would allow to give the rear wing a much higher angle of attack and to use the gap between them to refresh the rear wing's boundary layer like it is done in slotted flaps, so in combination their lift would be higher than that of one wing of the same area. The long, narrow propeller blades of this fictional aircraft look too flimsy, however, to be of much use in adding lift: They would break off at a fraction of their potential lift if built with existing materials.

  Without twist, can a propellor still
  provide efficient thrust? Could you reproduce the twist's effect by
  instead varying the length of the blade's chord from root to tip?

Good that you added "efficient"; this changes the answer from a "yes" to a "no". Only with twist would the local angle of attack be close to the optimum, but even without twist, thrust will be possible. Then the goal should be to pitch the whole propeller blade optimized for the outer 30% of its span. The thrust from this will create a strong root bending moment, however, and I doubt again that the slender prop blade will not break off. If you try to create thrust closer to the center, the outer part, which is flying at the highest dynamic pressure, will create substantial drag, requiring lots of torque, and again the propeller will break off, but in a different direction.

  Are there standard equations for calculating thrust and drag of a
  propellor that does not have twist? Or of a propellor in general?

Yes. The first good ones were published by A. Betz and L. Prandtl in 1919, and the latest substantial improvements were added by Larabee. Incidence can be prescribed, and so can be set constant over the whole span. If you can run a copy of Mark Drela's XROTOR, you can try for yourself.


Will the frequency 122.000 MHz no longer be used for Flight Watch after October 1st 2015? The Flight Service Program Changes announcement from the FAA includes

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

What are the “dedicated Flight Watch frequencies,” plural? The mnemonic drilled into my head was Flight Watch on 122.0, with the zero shaped like the face of a wrist watch.

The only frequencies I, a student pilot, have ever used for opening and closing flight plans has been RCO. The wording above is not specific, so does that mean instead of one dedicated frequency, you have to know the local RCO frequency to call Flight Watch?

Below 18,000 feet MSL, En Route Flight Advisory Service (EFAS) (a.k.a. Flight Watch) is provided on 122.0 MHz. Above this altitude, it is provided on discrete frequencies, with each one serving a specific ARTCC area (see AIM 7-1-5, FAA JO 7210.3Y Section 3).  These discrete frequencies are listed in the margin of IFR Enroute High Altitude charts:

To answer your original question, the FAA plans to consolidate EFAS onto existing Flight Service Station (FSS) frequencies on October 1, 2015. Because Lockheed Martin (the FSS contractor) has consolidated flight service stations, the EFAS weather briefers are now co-located with Flight Service personnel (they physically sit next to each other in the same room), making it possible to obtain both services on the same frequency.

At the same time, the FAA will phase out legacy Remote Airport Advisory Services and more significantly, require the ICAO format for all flight plans (international AND DOMESTIC), see Flight Service Program change announcement.


Why don't helicopter change altitude based on variable rotor RPM as opposed to the collective? AFAIU, helicopter rotors turn at constant RPM and changes lift based on the collective.  Why no have a variable RPM heli?

As some of the comments have mentioned, one of the major issues in using the rotor speed to adjust for lift instead of the collective is purely the speed of the response, but this is not the only one. Some of the issues that you will run into include

A large rotor blade will have a relatively large amount of inertia, which means that it takes a while to speed up or slow down the blade, and this is going to be prohibitive for safe flight
The rotor itself is attached to the engine via a clutch, which allows the rotor to spin freely if the engine quits. This is a requirement for auto-rotation, but it also means that you can't use the engine speed directly to slow the blade down, you'd have to include some sort of additional brake to slow it down if you want to maintain the ability to auto-rotate
Both piston and turbine engines, unlike an electric motor, have a significantly narrower/smaller range of RPMs that they can function at, with different amounts of power at different RPMs. The engines themselves are also limited in how quickly they can speed up and slow down, which means that even if you could speed up or slow down the rotors themselves rapidly, the engine might not be able to function at the required speed.
As the rotor size increases, so does the speed that the tip of the rotor is traveling at. If the tip of the rotor starts generating shockwaves because it has exceeded the speed of sound, you'll have significantly reduced lift and a large increase in sound volume. The tip of a small rotor isn't going to get anywhere close to super sonic, so this isn't a problem.
The tail rotor itself is mechanically connected to the main rotor, and will need to create different amounts of lift to control the yaw of the helicopter. Since you're probably not going to want to descend or ascend every time you turn left or right, you'll still need a variable pitch for the tail rotor. I already have to adjust the pitch of the tail rotor at various times, and it would add additional complexity to the piloting of the aircraft.
The rotor of a real helicopter is moving a much larger volume of air, and the pilot already has to manage the issues caused by it. For example, if I descend too quickly, I can descend into my own rotor downwash, which will not provide lift. If the wind is blowing in the correct direction, my rotor downwash can be blown into my tail rotor, which will cause a loss of tail rotor effectiveness. Having multiple rotors increases the complexity (and likelihood) of this occurring.

I'm sure there's a number of issues I haven't even thought of that would be difficult or impossible to overcome, but this is just the start. Most of these issues don't exist on a small drone because:

It has electric motors that have a much wider torque curve, and a much faster response time, so they can adjust the speed of the rotors quickly.
The rotors themselves have very little inertia, and their speed can be adjusted quickly.
There are multiple rotors, and no tail rotor, so you don't have the mechanical complexity associated with them.
Because of the significantly smaller amount of air that is being moved by a smaller aircraft, you have significantly less aerodynamic complexity. I don't think you're likely to encounter any issues with settling into your own turbulence, for example.
You can't auto-rotate. In a drone, it doesn't matter as much, since there's no one sitting in it, but as a helicopter pilot, I very much want the ability to autorotate.

This is certainly not a complete list of issues, but are just a small subset of issues that I can think of off the top of my head.


What is the concept behind being able to continuously pour iced tea while rolling an airplane? I recently saw Bob Hoover's famous video in which he is pouring tea while he is rolling the plane. Can you explain the physics that allow the tea to flow "up" when the plane is upside-down? Why doesn't the tea fall out of the pitcher like it would normally if turned upside-down?

The maneuver Bob Hoover is performing is a specific kind of roll called a barrel roll.  If you look at the path traced by this maneuver it is a corkscrew rather than a linear path that you might be imagining.  Because the airplane is rotating about a longitudinal axis as it translates forward there is centripetal acceleration toward the axis of rotation, or "up" in the reference frame of the person in the airplane.

To the observer in the reference frame of the airplane (e.g. the pilot or a passenger), the centripetal acceleration is interpreted as the fictitious centrifugal force.  This is exactly the same mechanism that you experience when driving around tight curves, though the force is in a different direction.  The end result in the airplane is that for a properly executed barrel roll, the centripetal acceleration causes the net force you experience inside the airplane to remain constant throughout the roll (in your reference frame, with the net force pointed "down").

If you were to close your eyes you would not know the plane rolled.  Likewise, the iced tea does not "know" it is upside down.  For a less dramatic demonstration, next time you are on a commercial airplane pay attention to when the plane is banking and turning and note that a cup of water on the tray doesn't notice the turn.  The cup stays in place and the fluid remains level (with reference to the airplane).

You can also demonstrate this with a small bucket and some rope.  Put some water in the bucket, tie the rope to the bucket and swing it in a circle vertically (be careful).  The water stays in the bucket if you swing it fast enough, and this is the same mechanism you see in Bob Hoover's video except it is the whole airplane being swung around in a circle like the bucket.


It is possible to feel a difference between helicopters with clockwise direction rotor and counterclockwise rotor? From the perspective of a pilot, is there a difference when flying a helicopter with a clockwise turning main rotor vs a counter clockwise turning main rotor?

Would a pilot notice if they flew the exact same helicopter except with an opposite rotation (and obviously all the corresponding mechanics mirrored.)

Yes, the pilot would certainly notice the difference.

When the engine applies clockwise torque to the main rotor, the body of the helicopter experiences counterclockwise torque. When the pilot increases collective to increase the amount of lift the main rotor produces, the engine will need to apply more torque to overcome the rotor's increase in drag. Therefore the pilot would have to apply right pedal to prevent the torque from turning the nose of the helicopter left.

If the rotor turned counterclockwise instead, these directions would be inverted. So if the pilot was flying the helicopter with the assumption that the main rotor turns in the opposite direction that it really does, he would tend to apply the wrong pedal and the helicopter would start yawing.


What is the name of the previous Air Traffic Management System (ATMS) of Hong Kong International Airport? Hi I really need help for the question.
The current ATMS for Hong Kong International Airport is the AutoTrac III, but does anyone know what is Hong Kong's Previous ATMS?


What is the difference between RFL and ECL in Air Traffic Control? There are two messages to change the Flight Level: RFL and ECL. However, I don't know the differences. Can anyone explain them?

RFL is Requested Flight Level, ECL is the En-Route Cruise Level. RFL the cruising flight level that has been requested by the flight plan or by the pilots, ECL is the level which has been actually assigned by the controller. The two may be the same or they may be different.

From the EUROCONTROL SPECIFICATION FOR TRAJECTORY PREDICTION Edition: 1.0, page 33

  2.3.2  Enroute Cruising Level (ECL) (3.3.2)

  Domain Knowledge: The  ECL   is  a  notional
  level  that,  in  the  absence  of  constraints,  equates  to  the
  RFL .  In  the  case  where  a  flight  is  not  permitted  to  cruise
  at  its  RFL   for  any  or  a  part  of  its  route,  due  to  the
  presence of a  strategic constraint (level limit) which applies to
  flights between the  aerodromes of  departure and destination, the ECL
  will be limited  to the level defined by the constraint. The ECL may
  also  be  changed  by  instruction from  ATC where  the flight is to
  maintain a different cruising  level, typically due to the proximity
  of a flight at the  RFL  on the same  route.   As with the  RFL ,
  the  ECL  can be changed for different  segments  of the  route  and,
  if different in  the  cruise  phase,  is  changed  to  the  XFL   on
  passing  the  sector   boundary.  The  notion  of  ECL ceases to exist
  after the final  TOD  from cruising level.

This is a complicated way of saying the requested flight level is usually assigned unless there's a good reason for the controller not to (to avoid potential conflicts for example), and the pilots can request a different flight level en route.


Is it possible to log IFR currency in a flight simulator without an instructor? A flight simulator system company has a system that they say lets you "Log IFR Currency without an Instructor." Can someone explain to me how exactly that works?

Does that mean that an Instrument rated pilot only needs a simulator to stay current?

Note: I am not a pilot so I don't know about currency requirements. I'm just curious.

UPDATE: 83 FR 30232, updated the requirements of 61.51(g) where an instructor is NO LONGER required to be present in order to log time in a flight simulator or aviation training device for instrument currency. Note that an instructor is still required in order to log simulator time that counts towards a rating or certificate and that a FAA approved device must be used. This particular change was effective July 27, 2018.

The following is no longer accurate, but retained for historical purposes:

There has been quite a bit of confusion in this area due to language in a preamble to the 2009 Final rule on Pilot, Flight Instructor, and Pilot School Certification, which implied that an instructor was not required for instrument currency and 14 CFR 61.51(g)(4) which says that an instructor must be present. I believe this all started with an email to John King of King Schools, where Lance Nuckolls at AFS-810 stated:

  ...approved uses for a BATD and an
  AATD are governed by § 61.4(c) and the LOA. The LOA states that an
  authorized instructor must certify the instructional use. Simply
  satisfying the requirements of § 61.57(c)(2) is not considered
  instructional use, therefore an authorized instructor does not need to
  be present.

(Emphasis added)

Interestingly enough, the PDF of this email is no longer available on the King Schools website. Instead users are redirected to the Rebird TD page where it now implies that an instructor is required to maintain instrument currency.  A copy of the message text is available here.

Of course, this was too much of a good thing, so someone had to get the lawyers involved! In Keller (2010), the FAA's Office of the Chief Counsel made their opinion known:

  ...in order to log the time an instructor must be present to observe
  an individual using a flight training device or flight simulator to
  maintain instrument recency experience.

This position was reasserted in Stewart (2014), which references the Keller letter and explicitly cites 14 CFR 61.51(g)(4).

So we now have a situation where the FAA doesn't agree with itself! Whose opinion wins?  The lawyers', of course! In Perry (2010), the Chief Counsel's office states:

  ...where two interpretations address an identical scenario and reach
  an inconsistent result, the interpretation issued by the Assistant
  Chief counsel for Regulations takes precedence.

Some additional background:

I believe the author is referring to the Redbird Flight Simulations' FAA approval page where it states:

  When using the Redbird to maintain instrument currency an instructor
  is not required to be present. This has been discussed with and
  confirmed by AFS-810. A current Instrument pilot is not required to
  have an instructor on board the real aircraft to log approaches in
  IMC, therefore it follows that the FAA trusts a pilot to correctly log
  an approach preformed in the Redbird.

On its face, this statement appears to be in direct conflict with FAA's legal interpretation. Of course, one could try challenging this position (an interpretation is an opinion, after all), but it won't be me!


Who made the first high-wing jet airliner? I thought the only high-wing jet airliners were made by the Soviets but the British Aerospace RJ-100 and Dash 6 series twizzled my mind.

So who made the first high-wing jet airliner?

Perhaps the Baade 152, built in Germany (GDR) in the late 1950s...
https://en.wikipedia.org/wiki/Baade_152


What means do airline ground staff have to converse with pilots in flight? It seems that airline operational staff on the ground have the ability to initiate verbal communication with airline pilots on at least some airliners, in flight.

Obviously pilots can communicate with ATC using, for example, VHF radio.

Perhaps, even in aircraft where phone service is not available to passengers, pilots in the air and/or airline staff on the ground can

initiate a voice call using telephony equipment that is separate from any PSTN (public switched telephone network)?

using existing headset?
using aircraft internal intercom handsets?
some means of selecting the call recipient?

send text messages over the data links (e.g. via ACARS (Aircraft Communications Addressing and Reporting System) through VHF (very high frequency) or SATCOM (satellite communication))?
use private VHF frequencies to communicate with airline operations?

If any of this is true, how does this work from the perspective of a pilot, steward or an airline operational staff member on the ground?

There are numerous methods for air-to-ground communications.  I may be missing a few, but off the top of my head, here are the ones I can remember:

normal VHF comms
Operational staff at the airport maintain an operations frequency that you can use just as you would would ATC.  The limiting factor here is the requirement of line-of-sight with the ground antenna and this limits range.  We could normally raise ops about 30-40 minutes out, at altitude, if someone was actually listening.  This is similar to a GA pilot calling unicom to arrange ground services.  This method is also used for maintenance at some stations and for talking to fuelers and deicing operators.
SELCAL
This is a selective calling protocol that operates over HF and VHF frequencies.  Each participating airplane and ground station (typically a dispatcher or ATC) has a code and if you know the code you want to communicate with, you can establish two-way communications with them.  To use this in the air required tuning a specific frequency and using a hand-mic with a keypad to dial the ground station code.  On the ground I'm not sure the exact method they use (phone patch?) but when they called us we'd get an aural "SELCAL" announced by the airplane along with a light to alert us.
AIRINC phone patch
This service provides VHF-to-PSTN patches and allows you to call your dispatchers actual phone, medlink, or anyone with a phone you feel like calling.  This worked by calling an operator over the normal radios and having them dial a number and connecting us together.
Satellite phone
Works just like any other satellite phone and use the Iridium network.
ACARS
This works just like text messaging.  Select your recipient, type a message and hit send.  You get alerts when messages arrive.  The interface I'm familiar with in the airplane is a program in the FMS with limited pre-set recipients you could contact (dispatch and perhaps a few others).  The ACARS software can also be setup to send specific messages to specific stations, e.g. an "In-Range" message which is routed to operations at your destination.  From the ground side, this is usually baked into the dispatch flight-following software.  Our dispatchers could right click on an airplane, get a menu, pick "text message" and type a message that would be sent to that airplane.


At what altitude, if any, may an ultralight overfly the Gallup airport (KGUP) with no prior authorization without violating FAR 103.17? At what altitude, if any, may an ultralight overfly the Gallup, New Mexico airport (KGUP) with no prior authorization without violating FAR 103.17?

This is a question about the meaning of

  "within the lateral boundaries of the surface area."

Resources--

FAR 103.17 --

  "No person may operate an ultralight vehicle within Class A, Class B, Class C, or Class D airspace or within the lateral boundaries of the surface area of Class E airspace designated for an airport unless that person has prior authorization from the ATC facility having jurisdiction over that airspace."

Sectional chart depicting KGUP

Description of the E2 airspace at KGUP-- from page E-116 of the FAA's "Airspace Designations and Reporting Points" document FAA Order 7400.11D--

  "ASW NM E2 Gallup, NM
  Gallup Municipal Airport, NM
   (lat. 35°30'41"N., long. 108°47'15"W.)
  Gallup VORTAC
   (lat. 35°28'34"N., long. 108°52'21"W.)

  Within a 4.1-mile radius of Gallup Municipal Airport and within 1.3 miles each side of the 242° radial of the Gallup VORTAC extending from the 4.1-mile radius to 4.9 miles southwest of the airport."

Note that no limitation is given as to the time of day that the E2 airspace is in effect, and therefore it is in effect 24/7.  No specific altitude limit is stated in this section, though on page E-1 we read--

  General.

  Generally, if the airspace is not Class A, Class B, Class C, or Class D, and it is controlled airspace, it is Class E airspace. Class E airspace extends upward from either the surface or a designated altitude to the overlying or adjacent controlled airspace. When designated as a surface area, the airspace will be configured to contain all instrument procedures. Also in this class are Federal airways, airspace beginning at either 700 or 1,200 feet above ground level used to transition to/from the terminal or enroute environment, and enroute domestic and offshore airspace areas designated below 18,000 feet MSL. Class E airspace does not include the airspace 18,000 feet MSL or above.

You can not fly an ultralight there without prior authorization if I am reading 103.17 correctly. The way that I am reading this, it seems that you may not be in controlled airspace around an airport without prior authorization, period. And, above  18000 is a no-go as well.

The highest concentration of aircraft traffic is at airports, Navaids like VORs, and on airways. You want to steer clear of those unless you are in clear and direct communication with those in charge of the airspace. Gallup has all three.

As far as Class E airspace, the way that 103.17 reads, It makes it sound like you are not allowed to fly in any Class E airspace over an airport without prior authorization. Admittedly, it’s splitting hairs. Everywhere else in 14 CFR, the description of Surface Class E has slightly different verbiage.

  103.17 Operations in certain airspace.
  No person may operate an ultralight vehicle within Class A, Class B, Class C, or Class D airspace or within the lateral boundaries of the surface area of Class E airspace designated for an airport unless that person has prior authorization from the ATC facility having jurisdiction over that airspace.

  137.43 Operations in controlled airspace designated for an airport.
  (b) No person may operate an aircraft in weather conditions below VFR minimums within the lateral boundaries of a Class E airspace area that extends upward from the surface unless authorization for that operation has been obtained from the ATC facility having jurisdiction over that area.

  3–2–6 Class E Airspace
  1. Surface area designated for an airport where a control tower is not in operation. Class E surface areas extend upward from the surface to a designated altitude, or to the adjacent or overlying controlled airspace. The airspace will be configured to contain all instrument procedures.


How is ACS different from PTS and when does it replace PTS for FAA certification? I've read some documents and articles that reference the FAA's new Airman Certification Standards (ACS) that will soon replace Practical Test Standards (PTS). What is different about ACS and when does it take effect?

The Airman Certification Standards (ACS) is basically an 'enhanced' version of the Practical Test Standards (PTS). According to FAA briefing on ACS,

  It (ACS) adds task-specific knowledge and risk management elements to each
  PTS Area of Operation and Task.

In general, while the PTS concentrates on what the applicant must 'do', the ACS specifies what he/she must 'know' and 'consider' (in addition to the 'do' part) to qualify for a given airman certificate or rating. The differences (in draft) are shown in this slide.

Image from Update on the ACS by FAA

According to the FAA briefing,

  • The “skills” section of the ACS covers the flight proficiency performance
  metrics in today’s PTS.

  • For each PTS Area of Operation/Task, the ACS lists the elements of
  aeronautical knowledge that support that skill.

  • In addition, for each PTS Area of Operation/Task, the ACS lists the risk
  management elements or behaviors associated with it.

The ACS is still under development, but FAA is targeting a June 2016 implementation (for airplane) depending on results of prototype (there is one running at the Embry-Riddle Aeronautical University) and some other factors.


On SIGWX (significant weather) charts, what does **/** mean? On SIGWX charts, it shows pairs of symbols with, say, */** or **/**. I know what the symbols mean on either side, but why are there two, and what does the slash indicate?

Would love good resources that explain more, too.

Example chart here, from the FAA sample questions (caution: 37 MB download), Figure 20, over Southern California.

I’m also interested in knowing what a dot with R underneath means.

http://www.beyourowncaptain.com/downloads/files/Reading%20Prog%20Charts.pdf
http://aviationweather.gov/static/adds/docs/metars/wxSymbols_anno1.pdf

Asterisks are snow, dots are rain. The slash means a mixture of the two.

The dot with an R under it is a substitution for the the thunderstorm symbol.

What you're looking at isn't a real SIGWX chart, it's a testing figure.


Is a CFI's 1st-time pass-rate based on the student or the instructor's first attempt? This question doesn't apply to anything I have done personally, and beyond word-of-mouth, I have no references about this happening.
Some people claim that if an instructor endorses a student and they fail an FAA check ride and then a different instructor endorses the same student for the re-take and then the student passes the re-take, that the instructor who endorsed the re-take may count this on his or her record as a first-time pass since the student passed on the first attempt for that instructor's endorsement.
The intended benefit of recording this would be utilizing it for CFI renewals and gold-seal CFI applications.
Is this a practice that is considered to be acceptable to the FAA?

I believe that your pass rate is based upon your number of students who passed on their first attempt after endorsement vs the number of students you endorsed for the checkride.  I don’t believe the FAA makes any other distinctions here, at least not for §61.197 requirements for the renewal of a flight instructor certificate nor for 89001, Section 13, Issuance of a Gold Seal Fight Instructor Certificate.


How do elevator servo and anti-servo (geared) tabs differ? (Community work) Image shows tab deflection direction in relation to an upward deflected elevator.

How do elevator servo and anti-servo (geared) tabs differ in handling? How to decide on which tab to use?

There is some confusion on the different types of tabs that can be found on aircraft: servo tabs, geared tabs, trim tabs.

The servo tab is an aerodynamic lever. It is connected directly to the pilot flying controls. When he moves the controls, he deflects the servo tab only, and feels aeroforces acting upon the servo tab only. When the servo tab deflects, it creates a force moment on the control surface ( elevator, aileron, rudder) which then deflects the control surface until aerodynamic moments are in equilibrium. If there is no airspeed, deflecting the servo tab has no effect on the control surface.

The geared tab changes the flight control forces to either increase them (usually in small aircraft) or reduce them (an arrangement used in the pre-hydraulic past of airliners). The control surface is directly connected to the stick/pedals - deflecting them causes the control surfaces to move. In order to alter control forces, a geared tab moves relative to the control surface:

For increasing stick forces, in the same direction as the control surface. Wiki and others mention anti-servo tabs, a less confusing name would be positively geared tabs.
For decreasing stick forces, in opposite direction of the control surface. Whether there is airspeed or not, the geared tab always deflects by a mechanical linkage when the control surface is deflected.

The trim tab has a constant angle relative to the control surface. The angle can be changed by extending/retracting a mechanical link, via a trim wheel or an electric motor with a screw jack.


How can one determine if a Service Bulletin is still applicable? I've seen the occasional Service Bulletin that is marked Obsolete, and others that Supersede SB-123. If I'm a pilot or A&P looking through logbooks, what resources are available to determine if a given SB still applies to the aircraft?

For example, American SB-131 applies to AA-1, AA-1A, and AA-5 aircraft. However, this scan (pdf) seems to suggest that it's obsolete, and the contents are now in the service manual.

This FAA AC outlines how SB's should be drafted. It also says that the Design Approval Holder should make available an easy way to search the SB's

A DAH should develop a robust SB/AD tracking and management system
using the following process to ensure overlaps and conflicts between
new and existing SB actions are identified and addressed: a. Search
capabilities should include the following primary areas:
(1)
Make/model or part number of affected product(s),
(2) Major aircraft
elements (e.g., engine, strut, wing, etc.),
(3) ATA code,
(4)
Maintenance zones,
(5) Service information (e.g., service bulletin
number),
(6) Airworthiness limitation sections,
(7) Previously issued
ADs, and
(8) Planned ADs (i.e., action(s) that the FAA proposes to
mandate in an AD).

This puts the ownership on the company a bit.
The FAA makes all current bulletins available here so you can check if they still list it as current.
There is also a bit of duality between service bulletins and Air worthiness directives. SB's are issued by the company if they feel there is a safety hazard to the aircraft. Most importantly, unless they are issued alongside an AD they may not be mandatory. You can check out this blog post that goes into it a bit more.


What happens to aircraft wreckage? A small private plane (Piper) crashed near where I live a few years ago. Both occupants were killed. The crash site is on the top of a ridge in dense forest. Reaching the site would require a hike of about a mile from the nearest road. The terrain is steep, heavily wooded, and crossing several creeks would be required. No vehicle can reach the site, not even ATVs.

I spent a number of years as an EMT with the fire department, so I know how the initial rescue goes and what happens to the human remains, but what happens to the wreckage and who takes care of it? The fire department certainly isn't going to invest the time and manpower it would require to haul that plane out of there.

In this example, you would have to use a helicopter to remove the wreckage. Even if you disassembled it on site, carrying it out would still be impractical (there's that engine to deal with, for one).

So for the investigators on a crash like this, do they travel to the site to inspect the plane, do they retrieve only key pieces, or do they just do without?

And to what extent does that depend on the size of the plane and number of victims? For example, do they leave the single-engine Piper where it is but haul out pieces of the 747 by helicopter?

Any info you'd like to add on salvage would be appreciated too. Crashed or not, a plane is likely to contain some valuable and undamaged electronics, engine parts, etc. Surely that stuff isn't just left for whoever wants it to salvage.

It depends on a lot of things like the kind of accident, the wreckage state, accessibility etc.
First thing to consider is that in most cases, the wreckage is evidence- so the investigating authority will take control of it and release it only when the investigations are complete or has reached a stage where the wreckage is not needed anymore.
As far as air investigations are concerned, the first thing to do usually is to dispatch a team to the site. For example, NTSB has a 'go' team which is dispatched as soon as possible to the accident site. From NTSB site:

At the core of NTSB investigations is the "Go Team." The purpose of the Safety Board Go Team is simple and effective: Begin the investigation of a major accident at the accident scene, as quickly as possible, ...
During their time on the "duty" rotation, members must be reachable 24 hours a day by telephone at the office or at home, or by pager.

After a preliminary investigation, the team decides what to do with the wreckage- either these are returned to the owner or retained for further investigation, partially or in full. From NTSB Major Investigations Manual:

When the IIC and the group chairmen have determined that parts or all of the wreckage is no longer needed for investigative purposes, the IIC ..., in consultation with the OAS Director, will be responsible for preparing and signing Part I of the wreckage release form (NTSB form 6120.15). The form shall be executed by the NTSB representative and signed by someone acknowledging his/her receipt of the wreckage This is done in almost ll cases, except those where there is no accessibility to the wreckage, like he ocean floor.
Part II of the wreckage release form will include a detailed list of any parts or components of the wreckage that will be retained by the NTSB for further examination.

Note that the release of wreckage is decided by the investigating authority and it may be kept in storage, if necessary.

There should be no pressure to release all of the on-scene wreckage. Often it is better to arrange for wreckage removal and storage and to retain control of the wreckage in case there is a need to examine it later.

In some cases, the investigating authority will go to great lengths to transfer the wreckage to their place, so as to carry out full investigation. This happened in the case of TWA 800 investigation, where the wreckage was picked up from seafloor and reconstructed to investigate criminal activity.

Image from the NTSB aircraft accident report (NTSB/AAR-00/03) fig. 29, page 102, via Wikimedia Commons.
Another thing is that the disposal of wreckage is a costly business when its done. This is where the size and location of the wreckage comes in. Most of aircraft wreckage would be aluminum scrap, usually too expensive to move and too uneconomical to use elsewhere. Obviously there's a difference between a 747 wreckage downtown and a R-22 wreckage in a remote hill (I'm taking about wreckage disposal, not investigation here). The disposal is done either by the owner/insurer or the investigating authority, with the owner/insurer coughing up. From Singapore Investigation of Accidents Statute:

If  a  person  to  whom  custody  of  the  aircraft, parts,  wreckage  or  contents  is  to  be released refuses to take custody thereof or fails to take custody within a reasonable period, the  aircraft,  parts,  wreckage or  contents  may  be  disposed  of  in  such  manner  as  the  Chief Inspector considers fit.
The  expenses incurred  by  the  Chief  Inspector  in  disposing  of  the  aircraft,  parts, wreckage  or  contents  shall  be  borne  by  the  owner  or  operator  of  the  aircraft  and  be recoverable from either or both of hem.

Most other countries have similar rules. As for reusing the contents in the wrecked aircraft, this is usually not permitted (though it depends on the operator/regulator rules). In case it is permitted, the LRU logbook should contain details about it being in an accident and in general, they are sent to OEMs for tests and recertificaiton. Some companies do trade in salvaged aircraft.
And finally the 'stuff' is sometimes left to salvage for whoever wants it- it may be the most economical thing to do, after all.


With current technology, why is there still increased separation between aircraft and delays in low visibility conditions? Since most (if not all) commercial aircraft are equipped with inertial and satellite/GPS navigation, why is increased separation between aircraft necessary? Can't controllers immediately identify the position and velocity of every aircraft?

In good weather, airports can move lots of aircraft because the ATC separation standards are much less than the bad weather, poor visibility ATC separation standards.

“Current technology” really hasn’t changed much over the years as ground based ILS CAT II and CAT III are still the most accurate ways to get get aircraft on the ground in bad weather.

Most of the increased separation is due to the requirements to have uninterrupted ILS ground signals reaching the aircraft on approach. Aircraft waiting to take off must wait behind hold lines farther from the runway, and aircraft on final must be spaced farther apart so as to not interfere with the ILS signals.

Once on the ground, aircraft will often experience delays getting to the gate due to the difficulty of taxiing in near zero visibility. Even parking at the gate can often require special standards and procedures.


What happens to manifold pressure reading following a reduction in both throttle and RPM? This was one of the questions in my online ground school quiz (PPL), detail as follows:

To set climb power, you reduce the throttle (manifold pressure) and then the props (RPM lever). After setting the props you expect the manifold pressure to:

A) not change
B) temporarily rises than fall again to where it was
C) fall slightly
D) rise slightly

My original answer was there is no net change in the MP reading after performing those two reduction actions.

My understanding of MP reading is that a reduction in throttle would mean more suction/vacuum as a result so the MP reading would decrease. On the other hand a reduction in RPM would mean less suction/vacuum so the MP reading would increase.

Because of the above, and that there is no other detail from the question as to how much changes each action had, wouldn't it be correct to expect MP reading to first decrease (from the throttle reduction) and then rises back again (from the RPM reduction). The net change therefore should be 0.

The correct answer however was d) slightly rises.
The explanation that was given is because the airplane was transitioning from take off power to climb power.

Why does MP rises slightly in this case?

I think you misread the question. Assuming you quote it properly,

  To set climb power, you reduce the throttle (manifold pressure)

… so the first step does reduce the manifold pressure and is therefore not subject of the question …

  and then the props (RPM lever). After setting the props you expect the manifold pressure to:

… only the second step is.

In the second step, the manifold pressure slightly increases, which

  On the other hand a reduction in RPM would mean less suction/vacuum so the MP reading would increase.

… you already understand.

So yes, the manifold pressure decreases first—when you retard the throttle—and then increases slightly as you reduce pitch. Just the question only targeted the second part.

The increase won't be back to the original value, because the throttle is still partially closed. With wide open throttle the manifold pressure is (for normally aspirated engine) almost ambient pressure and there is nowhere higher it can go.


Are there any manoeuvres that would be considered unrecoverable in a General Aviation / Training Aircraft? I'll try to make this question a little more manageable by applying the following constraints, though of course all answers would be welcome:

By "General Aviation / Training" aircraft, I'm talking primarily about normal SEP's of the kind that we see daily and would require no more than a check-ride before hiring. No experimentals, warbirds, super rare aircraft etc - though MEP's and Complex Aircraft would count.
I'm ignoring low level maneuvers. We all know a stall at 100ft is going to be tricky, though on the other hand, if something is going to require 5000' at a minimum to recover from then that's going to be fatal in most cases.
Let's ignore mechanical and airframe failures that occur prior to the incident.
I'm assuming Weight & Balance are within the normal category of the POH (As opposed to utility or aerobatic).

Beyond that, the question is what it says on the tin. Is there anything stupid that I can do as a Pilot in a Single Engined Piston GA aircraft that I simply won't be able to recover from, even with a few thousand feet to do so?

Yes, easily. Just fly fast enough.

If you deflect a control surface fully at a speed above $v_A$, the risk of a structural failure is very real. After all, at $v_D$ only a third of the mechanically possible deflection is allowed (see §23.441 for the rudder and §23.455 for the ailerons). Even combining full deflections of more than one control surface at $v_A$ is not covered, as is a repeated deflection in sync with rigid body oscillations which can create excessive loads. For a definition of the design speeds, see §23.335.

The regulations require minimum control forces so the pilot feels when he/she overstresses the airframe, but they are still within the strength of a normal adult.

Also, if you fly too fast in gusty weather, you can overload the structure. This is rare because the 25ft/s gusts which must be tolerated up to $v_D$ are quite uncomfortable to fly through.


What does an "X" at only one end of the runway mean? I came across aerial imagery of a dirt strip in northern Idaho with a white "X" at one end of the runway, but no markings at the other.  Does this mean the runway is only closed in one direction, or that it's fully closed and one of the markings is missing?

Google Maps image: https://www.google.com/maps/@46.0062134,-114.8435236,590m/data=!3m1!1e3!5m1!1e1

I think the X does mean that it is closed in that one direction.  If you look at the 3D view you will see that there is a mountain off the approach end of the X runway making landing on that runway virtually impossible.  If you were to depart on the other non-X runway you would have to turn relatively quickly to avoid hitting the mountain.


Can the safety of the Boeing 777 be extended to other models? It is becoming accepted that the Boeing 777 is the world's safest aircraft. There must be a reason for this of course, and aircraft designers should know it.

So my question is, can't we take all the safety merits of a B777 and copy them into other models and bring all airplanes to the same level of safety?

What's the "safest aircraft" depends in large part on who operates it, how they operate it, and where.

For many operators the 777 will be their prestige airliner, being assigned the most senior, most experienced, crews, the best maintenance, etc. etc..

That alone will mean less incidents and accidents than other types. They also have the range and ceiling to be able to fly around or over most serious weather. A 30 minute detour on a 10 hour trip can be made up, a 30 minute detour on a 1 hour trip in a 737 or A320 can't be (even if the aircraft would have the spare fuel to fly that detour).

The rest is mostly statistics. I seriously doubt there have been statistically more accidents per hour flown or per rotation on say an A340 as compared to a 777. There have been more airframe losses, but those include several lost on the ground due to them being stuck on airports in warzones (think what happened on Sri Lanka where Tamil separatist mortar bombs destroyed several airliners on the ground, damaging the until then flawless safety record of the type).

There have been AFAIK 3 777 hull losses (including the missing MH370) in flight.

Given the far higher number of say 737s in operation, and the far longer service history of that type, often with operators with shady operational procedures (more than a few are for example blacklisted by the EU) it's little surprise there have been more hull losses among the type. But comparing say the 737-900 only with the 777, with somewhat similar technology and number in service, as well as similar prestige level for crew assignments, you'll find a similar safety record.


Can I log instrument flight time for currency purposes in an Advanced Aviation Training Device (AATD)? Advisory Circular AC 61-136 which outlines the approval and limitations of flight training devices seems to contradict 14 CFR 61.57(c).

To what extent can I use an AATD for instrument currency? In addition, to what extent can an AATD be used toward and instrument proficiency check (IPC)?

Edit:

I have located this document from the FAA Office of Aviation Safety that clarifies that AATDs and BATDs are governed by FAR 61.4(c) and are authorized for specific purposes and can be used in the same manner at a Flight Training Device instead of a Aviation Training Device as long as they have an approve Letter of Agreement (LOA) from the administrator.

This leads me to believe that an AATD qualifies for FAR 61.57(c)(2) not FAR 61.57(c)(3).

From what I can tell, the Advisory Circular is outdated. It was issued July 14, 2008, while the most recent update to 14 CFR 61.57 was effective Nov 15, 2013.
When the AC was issued, 61.57(c) did not contain the wording specific to Aviation Training Devices (effective 11/17/2003). That language was added in the version effective 10/20/2009, and the AC apparently has not been revised since that point.
At this point the regulations are more specific (and regulatory) than the Advisory Circular. You should be able to log recent flight instrument experience in a ATD based on 61.57(c)(3), or the subsequent subsections that pertain to mixed currency.

(3) Use of an aviation training device for maintaining instrument experience. Within the 2 calendar months preceding the month of the flight, that person performed and logged at least the following tasks, iterations, and time [emphasis mine] in an aviation training device and has performed the following--

(i) Three hours of instrument experience.
(ii) Holding procedures and tasks.
(iii) Six instrument approaches.
(iv) Two unusual attitude recoveries while in a descending, Vne airspeed condition and two unusual attitude recoveries while in an ascending, stall speed condition.
(v) Interception and tracking courses through the use of navigational electronic systems.


What is the record for the highest achieved landing speed? The emergency landing of Hauptmann Siegfried Heltzel in a Lockheed F-104G Starfighter at the Nörvenich Air Base on 02 June 1965 is often mentioned as the record for the highest landing speed. The emergency landing became necessary after a mid-air collision with a Dornier Do-28. The landing speed is given as 435 km/h (270 mph). According to German-language sources, this value refers to touchdown; however, I didn’t find any source that mentions whether it corresponds to airspeed or ground speed.

Is this (still) the absolute record?

I am mainly interested in comparable parameter values of similar incidents in order to judge whether the above-mentioned emergency landing really was (or still is) an absolute record. Nevertheless, I would be glad about any information on possibly record-breaking incidents in closely related categories.

If that's the case, Hauptmann Hetzel was one uped by an Israeli F-15 pilot named Zivi Nedivi, who landed his jet with only one wing after a MAC with an A-4.  The touchdown speed was estimated to be at 260 kts (300 mph, 480 km/h).  That's the fastest landing I'm aware of where the pilot lived to tell the tale.

https://theaviationist.com/2014/09/15/f-15-lands-with-one-wing/

Now the highest known approach speed during normal operations, I believe, goes to the North American X-15 research aircraft/spacecraft, which crosses the fence at some 211 KIAS (242 mph, 388 km/h).

https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-052-DFRC.html

Also known to have very high approach speeds were the M2-F2, M2-F3, HL-10, and X-24A lifting body research aircraft with Vrefs in the 190-200 KIAS range.


Is aviation software translated into the users' native language desirable over English? I want to build some software containing information about aircraft, like a logbook. Nothing related with avionics.

I know that default language in the aviation industry is English, but in the case of online software, could professionals be interested in using an online logbook or MRO software showing in another language besides English?

English is the native language of aviation...
I myself always get mightily annoyed at poorly translated software, which is 90% of all software provided in multiple languages. IF you provide multiple languages, allow the user to switch between them AND get professional translators to do the work.

Would it sell? Probably, if it's good enough. But I don't see the language options as being a major selling point. Certainly not so big that having them will make a large number of potential customers choose it over another product that has more options elsewhere but lacks language selection.
In some places maybe, where English is less than common and not generally used by ATC.
Whether that's where your intended market is I don't know.


How do aerodynamic loads explain the Spaceship2 accident? From the NTSB's preliminary report, we read in the "Findings" section:

  Although the copilot made the required 0.8 Mach callout at the correct point in  the flight, he incorrectly unlocked the feather
  immediately afterward instead of waiting until SpaceShipTwo reached
  the required speed of 1.4 Mach.
  The unlocking of the feather during the transonic region resulted in uncommanded feather operation because the external aerodynamic
  loads on the feather flap  assembly were greater than the capability
  of the feather actuators to hold the assembly in the unfeathered
  position with the locks disengaged.

Taking into consideration that, as reported elsewhere:

  The vehicle's two tail wings are supposed to move when the spacecraft
  hits a certain speed, a maneuver known as "feathering." This
  repositioning helps to increase drag in order to slow the vehicle down
  for reentry.

From the article above, let's also take note of the visual depiction of such configuration change:

How is possible that this configuration change, meant to increase drag, needs a "preventing" (for lack of a better word) mechanism?
Since the repositioning helps to increase drag, how do the aerodynamic loads make the repositioning occour?
Wouldn't the (additional) drag on the tail section make it go back down again?

How do aerodynamic loads explain the Spaceship2 accident?

Aerodynamic load overpowered the actuators holding it in place, forcing it to open and causing SpaceShip2 to break up in flight. Although the rudders were unlocked early when SpaceShip2 was going at Mach 1.0, this action alone should not have been enough to pivot the tails upright, because neither pilot took the further step of turning the feather handle to actually move them. However, the tails rotated upward anyway, and the increase in drag at this point in the flight caused it to crash.

  How is possible that this configuration change, meant to increase drag, needs a "preventing" (for lack of a better word) mechanism?

The feather is ultimately there for re-entry. It acts as a hinge and can go up and down. This system increases atmospheric drag on the spaceship so that it naturally positions itself during re entry. To make sure the tail doesn’t move forward early, SpaceShip2 has a structural lock that holds feather in place. Around Mach 1.4, the lock is moved so that the feather is now mechanically free. It won’t move though because at Mach 1.4, aerodynamic forces keep it nailed back. In addition to the lock, the feather itself has a big actuator that drives it up and down. So just because it’s unlocked doesn’t mean it’s just flopping in the wind and it can go where it wants. In the (initial) boost phase, the aerodynamic forces can overcome that, which is why it is  locked .

  How do the aerodynamic loads make the drag naturally increase?

Aerodynamic forces are generated by the difference in velocity between the spacecraft and the air. There must be motion between the spacecraft and the air. If there is no relative motion, there is no lift and no drag. In order to maintain a constant airspeed, thrust and drag must remain equal, just as lift and weight must be equal to maintain a constant vertical speed. If in level flight, the engine power is reduced, the thrust is lessened, and the aircraft slows down. As long as the thrust is less than the drag, the aircraft continues to decelerate until its airspeed is insufficient to support it in the air.

Calculations can be found here

Aerodynamic forces are used differently on a rocket than on an airplane. On an airplane, lift is used to overcome the weight of the aircraft, but on a rocket, thrust is used in opposition to weight. Because the center of pressure is not normally located at the center of gravity of the rocket, aerodynamic forces can cause the rocket to rotate in flight. The lift of a rocket is a side force used to stabilize and control the direction of flight. While most aircraft have a high lift to drag ratio, the drag of a rocket is usually much greater than the lift.

  Wouldn't the drag on the tail section make it go down again?

There are two conventional ways to transition from space back to Earth: One is to come in as a winged airplane, like NASA’s space shuttle. In this way the spacecraft can land where it wants, but hitting the perfect angle of attack is tricky. The second method is as a capsule, which is essentially dummy-proof, but has no control over where it lands and subjects its occupants to high G-forces. SpaceShip2 is a bit of both. Its tail folds up and down, changing the vehicle’s shape from something that falls like a capsule to one that flies like an airplane once it’s back in the atmosphere.

Each of the two tails acts as a rudder, and has a small, horizontal flap at the back, extending to the outside. When the plane is descending, both tails can pivot upright, together, from 0 to 90 degrees, so that they stand “vertically” behind the plane. In this configuration, the tails and flaps create drag. When pointed upward, the tails are at right angles to the direction of airflow, creating a huge amount of drag on the vehicle, which slows it down without overheating the spacecraft. This method works because SpaceShip2 is not coming back from orbit.If put in feathered configuration during powered flight, the drag vector and thrust vectors are horribly misaligned, resulting in extreme pitch rates and, since the aircraft wasn't built to withstand those stresses, it would break apart


Do Jet-A and 100LL smell different? Recently, a small plane operating from a nearby airport suffered an engine failure on takeoff and crashed.  One of the hazmat responders dealing with the resulting fuel spill mentioned "a strong smell of Jet A", leading to speculation that the airplane had its tanks filled with the wrong fuel.  Would he have been able to distinguish Jet A from 100LL by smell?

If you know what you're looking (sniffing) for, yes.

Avgas 100LL smells like gasoline (a little different than what you pump into your car, but similar).

Jet-A smells like kerosene (not quite "like diesel", but definitely not like gasoline).

If you are familiar with how both smell you can tell them apart by odor, and a significant contamination of Avgas with Jet-A could be detected by smell. (Other tests, like an evaporation test, are more reliable for lower levels of contamination however).


What do air traffic controllers do on a slow day? We all know air traffic controllers have one of the hardest, most stressful jobs on the planet... day after day they handle thousands of aircraft with the cool of a seasoned gunfighter and the surgical precision of a Jenga-playing robot.

But what about when there's no aircraft around? Perhaps it's freezing rain and there no chance of an aircraft landing. Or perhaps the (extremely) high volume of flight training at a particular field suddenly drops to nearly zero over spring break. Or maybe fate and luck just got together and no one wants to go to that airport today.

What do controllers do when there's no aircraft in their area, and especially what do they do when there's not likely to be any aircraft for an extended period (1+ hours)

The airspace around the world is divided into sectors within a Flight Information Region (FIR) /Air Route Traffic Control Center (ARTCC) / Area Control Center (ACC), which range from very small and tight airspace pieces to larger combinations or enroute sectors. Enroute sectors will usually be larger than Terminal Maneouvering Areas (TMA).

During peak-hours, these sectors will be handled by one controller responsible for each sector. If capacity and traffic flow permit, these sectors can be combined and two sectors will be handled by the same controller.

Below is a picture of the Paderborn Lower Sector, ranging from GND to FL135. This is usually a stand-alone sector which only covers approaches to Paderborn (EDLP) and Dortmund Airports (EDLW).

(Image Source: Own Work - Author: SentryRaven)

If traffic permits, the adjacent sector Hamm Lower from GND to FL115, handling arrivals and departures to Münster (EDDG), will be handed over to the controller responsible for Paderborn Lower. This can also be done vice-versa, where the Hamm Lower controller becomes responsible for the Paderborn Lower sector.

(Image Source: Own Work - Author: SentryRaven)

TMA controllers not only handle IFR aircraft approaching or departing from airfields within their sector, but also any enroute traffic crossing the sector, VFR traffic requesting to cross airspaces which require prior permission and other tasks.

As Chatty already pointed out in his answer, controllers take breaks between working their sectors and sometimes often switch sectors during a shift. A controller working Paderborn Lower during the beginning of his shift can end up working Hamm Lower towards the end of his shift with adequate breaks in between their sessions.

See this related question:
What is the maximum number of planes a controller can control?