Which Terminal Arrival Area depiction is correct between NACO and Jeppesen plates? Looking at the RNAV (GPS) 19R into Wichita, KS (KICT), the TAA arrival segments are drawn differently between NACO and Jeppesen plates.  Please take note that the TAA arrivals on NACO charts show both the IAF and IF fixes on the arc segment while Jeppesen charts only show the IAF fix.

Which depiction more accurately depicts what the pilots are expected to do from ATC and when would a pilot ever perform the hold in lieu of procedure turn at ACUBO?

Thanks

I'm not familiar with Jepp plates but as far as I can see both plates are the same, it's just that Jepp chose not to depict ACUBO on the base area icons (as the FAA calls them). I assume that's to reduce clutter on the chart but I don't know for sure. In any event, I don't see how it would change the procedure in any way: all the fixes are still shown on both plates, and all the details seem to be the same.

As for the HILPT, the rule for procedure turns is that by default you have to fly them unless you have a valid reason not to (see this question). In the case of this approach, the plate says NoPT if you're approaching from the straight-in area or on the direct tracks from CADAC/BEBAC to ACUBO. If you get to ACUBO any other way, you have to fly the HILPT. The most likely reason would be that you're coming from the south and ATC vectors you directly to ACUBO rather than to CADAC or BEBAC: "N12345, proceed direct ACUBO, cleared for the RNAV 19R approach".

The FAA Instrument Procedure Handbook (chapter 4, p. 4-58) has detailed information on TAAs, including this:

  ATC may clear aircraft direct to the fix labeled IF/IAF if the course
  to the IF/IAF is within the straight-in sector labeled “NoPT” and the
  intercept angle does not exceed 90 degrees. Pilots are expected to
  proceed direct to the IF/ IAF and accomplish a straight-in approach.
  Do not execute HILO course reversal. Pilots are also expected to fly
  the straight−in approach when ATC provides radar vectors and
  monitoring to the IF/IAF and issues a “straight-in” approach clearance;
  otherwise, the pilot is expected to execute the HILO course reversal.

But even if ATC vectors you to ACUBO they can't give you a straight-in clearance if your intercept angle is greater than 90 degrees (ATC Orders 4-8-1(d)
 and (e)).

You also asked in a comment what happens if ATC clears you for the approach without specifying the IAF. That's explained in the IPH:

  On rare occasions, ATC may clear the aircraft for an approach at the
  airport without specifying the approach procedure by name or by a
  specific approach (e.g., “cleared RNAV Runway 34 approach”) without
  specifying a particular IAF. In either case, the pilot should proceed
  direct to the IAF or to the IF/IAF associated with the sector that the
  aircraft will enter the TAA and join the approach course from that
  point and if required by that sector (i.e., sector is not labeled
  “NoPT), complete the HILO course reversal.


How do pilots decide whether or not to deploy a ram air turbine? Since the turbine needs to be deployed from within the aircraft to the outside, it will obviously induce aerodynamic drag (slowing the plane down?).

I mean I remember reading an article where a plane that for whatever reason did not stow it's landing gear and ending it burning significantly more fuel than planned.

So my question is what checklists and other factors to pilots need to account for before they decide to deploy the RAT

The reason why the RAT deployed is of primary concern. The RAT should automatically deploy when (depending on the design of the aircraft) you lose all primary electrical and/or hydraulic power. In these cases, an immediate diversion is necessary because you may be one failure away from losing control of the airplane.

However there are uncommanded RAT deployments due to system malfunction, or mistake. For example, the pilot hit the RAT button by accident, or somebody accidentally switched off both generators instead of switching on both bleeds. In that case, the problem is easily rectified and then the pilot needs to decide whether to divert/return or continue the flight.

For Airbus, they state

  The uncommanded extension of the RAT is not considered to have any additional operational impact. The RAT is able to be extended in all flight envelope conditions. If there is an uncommanded RAT extension, then this is indicated to the flight crew, and hence the appropriate maintenance action, i.e. the resetting of the RAT, can be performed.

Fuel burn is minor, I think its +1% on the A320 family. The main concern operationally is that a RAT is loud. They sound like a prop plane or helicopter, so for passenger concerns, you might end up landing and having it restowed.


How can some stretched derivative airplanes have longer range while most have less? On the one side A321 neo has almost the same range as the A320 neo (250 NM difference), and a LR version of A321 neo will have an even longer range. The same goes for  the Dassault Falcon 7x and the longer and longer-range Falcon 8x.

On the other side Boeing 737 MAX line shows a clear tendency: the longer the fuselage the shorter the range. The same tendency can be observed on most aircraft types.

I understand that fuel is generally in the wings which keep the same volume on a stretched derivative, but fuselage can accommodate fuel tanks and range can be a crucial point for aircraft. So why don't/can't aircraft manufacturers propose equivalent range stretched aircraft in general, as the A321 neo does?

When aircraft are stretched, they usually just receive extra fuselage plugs on both sides of the wing: wing redesigns are incredibly expensive and take a long time. So the longer aircraft has a higher empty weight, and due to the unchanged wing design the fuel capacity remains the same - this reduces range. The aircraft is fuel limited. Conversely, if fuselage plugs are removed the same amount of fuel can take the aircraft further, as the B707-138 demonstrated, Qantas' first jetliner.

The A321NeoLR fixes the fuel limitation by adding extra fuel tanks in the cargo bays as this article explains, so that the aircraft now becomes weight limited. The extra fuel means that there can be less extra revenue from cargo. The B737-9 cannot follow suit, because it is has a shorter landing gear and has rotation limitations: from this article:

  737 MAX9 is not suitable for stretch to an international version, not because the wing is not good enough but because the MAX9 cannot bring the wing to an angle at take-off where it can work efficiently; the landing gear is too short.

The longer fuselage limits the rotation angle before a tailstrike occurs, so max. TO weight has a hard limit that cannot be managed by trading cargo weight for fuel weight. Above photo is from this site, which also contains a table with geometric angle limitations for the different 737 versions: the -9 has a tail strike pitch attitude of 10 deg, and has increased flap deflection of 25 deg to limit lift-off attitude to 6.8 degrees. A small variation in centre of gravity at a high TO weight can cause a tail strike.

Boeing has launched the B737-10 which will address the rotation limit by a redesigned landing gear.


What are the major drivers of cost/price differences between Cessna 172 and Piper Cherokee? This may be closed as opinionated but I'm looking for answers with hard data if I can get them. The Cessna 172 and Piper Cherokee are touted as two of the most successful light aircraft designs in the world, and they are primary competitors, with Piper originally designing the PA-28 Cherokee to be a lower-cost version of the Comanche that would compete directly with the 172 of the day.

However, in today's new market, a 2015 Cessna costs about \$370k, while Piper Archers (the continuation of the PA-28 airframe after Piper's corporate restructure) made in the last 10 years or so are selling for about \$200k. Cessna also seems to hold more value; "classic" 172 airframes from the 70s and 80s hold about a \$100k value in classified ads, while flight-ready Cherokees from the same time can be had for \$30-40k and a few Cherokee airframes are being offered at prices I've only ever seen 150s sold for (though there's likely something wrong with those examples).

The aircraft, while different externally (the 172's overhead-wing versus the Cherokee's low-wing design is the biggest difference), seem to have many similar specs on paper; passenger count, horsepower variants (Piper's actually better here as the 180hp variant was most common compared to the standard 172 powerplant at 160hp), instrument capabilities, etc. Cockpit pictures indicate the interiors are comparable; a bit dated as you'd expect from aircraft made 30 years ago, but perfectly serviceable.

So the question is, where's the additional retained "street value" of the 172 coming from? Is the 172 more well-reputed for safety or reliability? Are its handling characteristics considered better for everyday flight (perhaps due to the parasol wing)? Is this a question of average age of airframes? Is it just the Cessna name (in other words, am I comparing a Toyota Camry to a BMW 5-series)?

Obviously some of this stuff will depend on a comparison of specific hulls, but there's a definite trend; the market in general seems to value the 172 more highly than the PA-28 with all other things being equal on paper. The question is why.

There are a lot of factors here but in reality a 172 and a Cherokee are about the same price, lets look the reality.
First off a huge chunk of people rent instead of buy. In this regard at the two airports I have been flying out of have both the 172s and Cherokees (both of which I have rented) are the just about the same exact price (all prices in USD).

Cherokee Wet  : 108
VFR Only 172: 103
IFR 172 : 113

The used prices (how a lot of people buy planes like this) span the field and I would say are on par (as per my latest perusing of Trade-A-Plane). That being said you can get a beat up Cherokee 140 for in and around 20K and a beat up 172 for about the same price (at least from what I have seen listed). At the same time you can get a fully loaded Cherokee 180 or 235 if you go complex with dual GPS/COMS and other toys for the better part of 60-70K, same for the 172s.
Yes they are similar planes but the truth is that the price things actually trade hands for is often not disclosed and is almost always not the list price in terms of used stuff. There is a bit of preference as well, if you trained in a Piper you may be more inclined to stay in a Piper and likewise with the Cessnas.
As for safety, the 172 is a very safe plane by anyone's standards. Then again so is the Cherokee and it seems that the argument can go on forever but the numbers are the numbers (accidents per 100,000 hours of flight)

The 172: 6.17 overall accident rate.
The Cherokee: Cherokees came in at 6.86

In reality a small difference, but lets be honest they are about on par. For what its worth, the Cherokee numbers include the Arrow which is a retractable and suffers from the proverbial gear up landing as well as other things that make a retractable potentially fail more than a fixed gear plane. This may account for the difference in safety record (again, a very slight difference).
While similar on paper there are some mission profiles that allow the planes to serve different roles and may make the 172 more attractive in some cases. The high wing design allows for excellent downward view which makes the 172 a great plane for aerial surveying/photography/pipeline check ups and similar tasks. The 172 also sports two doors compared to the single one on the Cherokee. That being said some feel as though the 172 is a bit easier to get into for the less nimble, but I am young and nimble so I can't speak to this. There are also those who like the high wing design for landing on grass or other back country flying due to the increased ground clearance of the wing allowing you to avoid obstacles.

From an aircraft family standpoint the Cherokee 235 had a much better useful load than the highest power 172's. However even the 180 Cherokee has a better useful load than the 180 Cessna. When you are flying around a family this is worth considering.
Although Cessna had it to an extent, Piper has always had the selling point of "stepping up through the planes". The idea being that your mission (as time went on) would be to go faster, further, and higher. Subsequently you would need a bigger plane. They facilitated this by delivering a very constant platform in the, Cherokee, Arrow, Cherokee 6/Lance/Saratoga then up through twins with the Seminole and Seneca if you need to go there. While I'm not sure I have ever seen any real data on this, I do have a real world experience with a buddy of mine who has been flying for about 25 years.
In response to the question "Have you ever owned any other planes?"

Yeah, I had an Archer for a while, it was a great plane. But then I had a third kid so I bought a Saratoga.

Like it or not the Piper sales model there worked.
You could also forgo common sense and just buy a Mooney because everyone else put the tail on wrong.


Is the entire length of a B747 or A380 wing used as a fuel tank? It is generally understood that the fuel tanks of aircraft are in the wings, but specifically, is the entire length of the the wing of:

an Airbus A380 Jumbo used as fuel tank?
a Boeing 747-800 Jumbo used as fuel tank?

What percentage of the wing length is used as a fuel tank and for what reasons, for:

an Airbus A380 Jumbo
a Boeing 747-800 Jumbo

Fuel tanks take most of the space in aircraft wings, but not all. There are other things on wings too. They are ailerons, flaps, slats, air brakes. On most airliners, the engines are attached to the wings too, so their assembly takes up space.

On the two aircraft of your interest, here are the pictures:

A380 (its nickname is not jumbo, but superjumbo)

Image Source

747

Image Source


What classification of aerial vehicle would a manned quadcopter or octocopter be? US here, if it makes a difference (w.r.t. FAA regulation, etc.).
There's a new upcoming class of aerial vehicles, similar to drones, however they are gigantic and they are manned -- that is, manned (piloted) quadcopters or octocopters like these ones.
I'm wondering what technical and/or legal classification(s) these types of vehicles would be considered to be. Any thoughts? Thanks in advance!

From 14 CFR 1.1:

Helicopter means a rotorcraft that, for its horizontal motion, depends principally on its engine-driven rotors.
Rotorcraft means a heavier-than-air aircraft that depends principally for its support in flight on the lift generated by one or more rotors.
Aircraft means a device that is used or intended to be used for flight in the air.

A manned quad- or octocopter seems to fit the definition for “helicopter”, assuming you mean the kind that have no fixed wing.


What do the terms 'holding out' and 'common carriage' mean? A pilot with a new commercial certificate is excited at the new world of getting-paid-to-fly they have opened up.  That is, until their instructor or good friend reminds them of 14 CFR 119 and the grey line that separates operations that do or do not require an operating certificate.

It is cut and dry that a commercial pilot can be paid to do certain things, but when you decide you are going to start doing things for a friend ("yea, I can transport XYZ for you on my next trip to Kalamazoo") things start to get murky. Especially once your friend starts paying you, you make a habit of transporting things and he tells his friends about your service.

At what point are you holding out your services to the public and when do you cross the line from private carriage into common carriage?  How far can you go without an operating certificate.

I'm looking for regulatory answers or anything written from a FSDO, basically anything not anecdotal.

Oddly enough, "common carriage" is not defined in the FAR's, but that is because it is a "common law term" and not specific to aviation.

AC120-12A - Private Carriage Versus Common Carriage of Persons or Property contains guidance that can be used to help determine whether or not an operation falls under common carriage.  Take a look at it for specific examples, but the "plain language" version is:

Common Carriage: A carrier becomes a common carrier when it "holds itself out" to the public, or to a segment of the public.

Holding Out:  A carrier is holding out when they represent themselves as willing to furnish transportation within the limits of its facilities to any person who wants it.

There are lots of ways to "hold out", but the basic idea is if someone in the general public comes to you and asks you to fly them and you agree, you are probably holding out.  Any form of advertising demonstrates a clear sign that you are holding out.  There are also other activities that qualify, so look over the AC if you have further questions, and if that doesn't answer it your best bet is to contact an aviation lawyer.  You could also contact your local FSDO with questions.

As far as transporting a third part for hire, both common and private carriage require an air carrier certificate issued under 125 or 135 depending on the size of the airplane1. This means that your trip for a friend would be in violation because you don't have the required air carrier operating certificate.  (Thank you @p1l0t for clarifying this for me!)

119.23 says:

  Operators engaged in passenger-carrying operations, cargo operations,
  or both with airplanes when common carriage is not involved.

  (a) Each person who conducts operations when common carriage is not
  involved with airplanes having a passenger-seat configuration of 20
  seats or more, excluding each crewmember seat, or a payload capacity
  of 6,000 pounds or more, shall, unless deviation authority is issued--

  (1) Comply with the certification and operations specifications
  requirements of part 125 of this chapter;

  (2) Conduct its operations with those airplanes in accordance with the
  requirements of part 125 of this chapter; and

  (3) Be issued operations specifications in accordance with those
  requirements.

  (b) Each person who conducts noncommon carriage (except as provided in
  Sec. 91.501 (b) of this chapter) or private carriage operations for
  compensation or hire with airplanes having a passenger-seat
  configuration of less than 20 seats, excluding each crewmember seat,
  and a payload capacity of less than 6,000 pounds shall--

  (1) Comply with the certification and operations specifications
  requirements in subpart C of this part;

  (2) Conduct those operations in accordance with the requirements of
  part 135 of this chapter, except for those requirements applicable
  only to commuter operations; and

  (3) Be issued operations specifications in accordance with those
  requirements.

The FAA takes a very dim view of people who start competing with actual air carriers and are unlicensed to do so.  It's a quick way to have your license suspended and end up with some hefty fines and other legal troubles.

1 There are of course the regulations that allow operations "in furtherance of a business" which is why I specified a third party.


How are off-wing jet engines transported? One of the optional services in Rolls-Royce TotalCare is "Engine Transportation"

  This service includes routine transportation of engines between the customer’s main base (or designated station) and the engine shop, and/or remote site transportation.

Jet engines can be very large heavy and expensive items. How are they transported? Are they flown or do they use road transport? Are there dedicated vehicles?

They have the usual transport options: shove into cargo area, on a flatbed truck, shipping container,...

They can also be attached below the wing of a large aircraft and flown with if there is no room in the cargo area.

(stolen from this question)

Notice the extra engine on the near wing.


Why does thrust-to-weight ratio depend from max Mach number? Why, for jet airplane design, does maximum Mach (or maximum speed) affect thrust-to-weight ratio so strictly? (as you can see for example in Daniel P. Raymer "Aircraft Design: A conceptual Approach" Table 5.3 page 80, where you can find $\frac{T}{W_o}=a\cdot M_{max}^C$, where “$a$” and “$C$” are empirical factors, for jet transport $a=0.267$ and $C=0.363$)

Just now I did notice to detail that Raymer say : "The equations were developed by the author using data from Ref 1" Ref1: i.e. the famous annual book : "Jane's All the world Aircrafts" . But anyway "maximum speed" (or maximum Mach number) in this case the maximum speed is ...the speed that the aircraft is not able to exceed  or.... the speed that is forbidden for the pilot to try to exceed because it can be dangerous? Because, if it's the first case it's more understandable; in fact, if the other parameters are fixed, with the same fixed distance, if T/W is low the acceleration is lower and so before the end of the distance, you can arrive to low speed. At the opposite if T/W is high the acceleration is higher and so before the end of the distance, you can arrive to high speed. What do you think? So, in Janes book, what is the definition of Maximum Mach number?

Disclaimer: I have no copy of Raymer's book, so I have to guess what this table looks like.

There should be no direct dependency, except that all aircraft need to operate in the real world. If you look at the wing loading of regular jet transports, you will notice that they bunch together around 500 - 600 kg/m². This is the maximum wing loading which still allows them to operate from normal airports - go to higher values an you need a dry lakebed for take-offs and especially landings.

To push the resulting wing to higher flight speeds needs more thrust - hence the dependency. If you start with a higher wing loading (say, 800 kg/m²), the thrust/weight ratio for reaching the same Mach number is lower. The approach and landing speeds grow with wing loading as well, which in turn affects the resulting landing distance. I guess there is a maximum landing distance requirement for all aircraft in the table which is not explicitly mentioned.


What do de-icers do during summer? I was reading about plane de-icing the other day, and someone posted a comment saying that was their job, and when no planes needed de-icing they just slept/waited in the de-icing truck.

I was looking just now at de-icing jobs, and found one at heathrow that said it was a permanent 40-hour/week job.

So what do they actually do during summer? Do they do a different job or do they just wait in case a random (unlikely) snow storm passes by?

Most de-icers are run by the airport FBO so the people who work on de-icing in the winter work on other FBO duties such as refueling and the like when there is no de-icing to do. Some de-icers are just hired permanently for winter times.


Do smaller wings mean faster flight? I've known that military aircraft with small wings can fly very fast, while commercial aircraft with big wings cannot fly as fast. Why is this?

On the whole, smaller wings produce less drag, but they also produce less lift. Less drag means the same engine can reach a faster cruise speed, but less lift limits the weight capacity and means the aircraft needs to go faster to stay airborne: the stall speed, take-off speed, and landing speed will all be faster, which in turn means longer runways are needed (or systems like catapults and landing chutes).

For a fighter aircraft, that top speed matters a lot more than the lifting capacity or take-off speed, so they're optimised with these low-drag, high-lift wings. Compare to a utility aircraft of the same size: the utility aircraft will have a less powerful engine, and wings that produce more lift at lower speeds. A utility aircraft that needed the same kind of runway as a fighter would be pretty useless.

In the other direction, compare to an airliner. These wings are tuned like a fighter's: to be maximally efficient in the cruise. But the airliner has to lift a lot more weight, so the whole aircraft is much larger, and the wings are in proportion to that. They typically also require long runways, and fly faster than a small utility aircraft. But look at the Hercules military transport. It's designed to lift a lot, but it also needs to operate from poor-condition, short runways. It has less efficient, high-lift wings, so its take-off speed is very slow for its size, and it isn't that fast in the cruise.

In summary, wings (not just wingspan, but also the shape of the wing) allow you to trade off lift and drag. High lift and drag gives you slower take-off and landing speeds, but you pay for that with a less efficient cruise. Low lift and drag gives you a faster cruise, but you pay for that with ridiculous take-off and landing speeds and the extra runway that requires.


How to adjust the center of gravity of an aircraft if not level when being weighed? how do you adjust the center of gravity when weighing an aircraft in not-leveled position using platform scales under the nose and the main gears, and dropping a plumb bob to mark the gears locations.

I drew in the approximate location of the screws used to hold a level while leveling the Cessna Cardinal for weighing.

When my plane was weighed, they had to lower the nose by deflating the nose strut some, and raise the main gear, to get the aircraft to the level position indicated by the manual, with a level across the leveling screws on the side of the fuselage. I don't know that there is a procedure to weigh it in a not-level position.


Has an airplane ever been launched from a train? Presumably helicopters have landed and lifted off railroad flat cars.

Has an airplane ever been launched from a train?

(my artwork)

F-84 during project ZELL testing (info provided by jwenting)

It's not a train, but Brendan O'Brien (with the O'Brien Flying Circus) has an act where he lands a Piper Cub on a moving trailer, towed by a car. There are some YouTube-clips showing this, including a take-off (around 1:50). Regarding your earlier comment on 'as close at it gets': I think this is it.


Why might a Cessna 208 need a FAR Part 23 waiver? The capacity of the Cessna 208 is stated as 9 passengers, or up to 14 with a FAR Part 23 waiver. FAR Part 23 states that it applies to any aircraft with "more than 10 occupants and that is intended for use in operations under Part 135" (commuter or on-demand operations).

What part or parts of Part 23 require the C208 to have a waiver?

Is it common for waivers like this to be issued for the C208 or in similar situations on other aircraft?

The Cessna 208 is a bit of a confusing model when it comes to seating.

Short version:

Under US legislation, the aircraft may have up to 11 seats and can carry 9 passengers and 2 pilots. Other countries did recertify the aircraft to have up to 14 seats. By doing so they adopt the FAA certification based on part 23 and add text to waive the 9 passenger limitation.

Long version:

Originally the type was approved by the FAA in October 1984 under FAR 23 (up to amendment 28) and given FAA Type certificate number A37CE. The aircraft is certified as 11 Place Closed Land Monoplane (PCLM) and later as 11 Place Closed Sea Monoplane (PCSM).

In 1984 the applicability of Part 23 was described by 23.1 (since amendment 10) as:

  (a) This Part prescribes airworthiness standards for the issue of type
  certificates, and changes to those certificates, for small airplanes
  in the normal, utility, and acrobatic categories that have a passenger
  seating configuration, excluding pilot seats, of nine seats or less.

So this is where the 9 passenger limitation originally comes from. This also implies that if you operate with only one pilot, one of the 11 seats must be unoccupied.

Until 1971 there was no mention of a 9 passengers limitation and since 1987 (amendment 34) a new category of commuter planes is defined allowing for more than 9 passenger (up to 19 passengers) in propeller-driven, multiengine airplanes.

Since the Cessna 208 is a single engine aircraft, the commuter category cannot apply. As a result, when the aircraft is operating under the FAA type certificate, there is a limit of 9 passengers.

When the aircraft is registered and operated outside the USA, the FAA rules do not necessarily apply. Usually a country adopts the Type Certificate of the original certifying country, but changes can be made. This is exactly what happened with the Cessna 208.

Since the aircraft offers space for more seats and the maximum take-off weight allows for extra passengers, Cessna started to offer a 14 seat model for use outside the USA.

For aircraft with more than 11 seats, the flight manual has a supplement stating:

  Limitations

  Utilization of the 13-place, 14-place and Utility seating options
  described in this supplement is limited only to nations where approval
  has been received. The United States does not authorize more than 11
  seats in the airplane. In the 11- seat configuration, the right front
  seat may be occupied by either a second crew member or a passenger,
  However, when the right front seat is occupied by a passenger, only
  eight seats in the aft cabin can be occupied.

Europe (EU)

The EASA Type certificate allows the 11 seat model 208. It also mentions a 14 seat model 208B being approved by the UK CAA. When EASA took over aircraft certification in Europe, the UK CAA approvement for 14 seats was adopted, but only for the 208B model.

In section 2.E (only for 208B):

  A 14 seat place configuration was certified before 28 September 2003
  by CAA UK (see UK TCDS FA54) and subsequently adopt by EASA. Those
  aircraft have to be operated i.a.w. FAA approved AFM 1329-3- 13PHUK
  and AFM Supplement D1340-1-13UK or latest approved revision.

The original UK CAA approval included the text:

  MAXIMUM OCCUPANTS/PASSENGERS: 14 occupants, including pilot. Refer to
  British Aeroplane Flight Manual

Australia

The type certificate for the Cessna 208 mentions:

  Australian registered Cessna 208 aircraft may be configured for
  greater than 9 passenger seats. The requirement of FAR 23 paragraph
  23.1, introduced by amendment 23-10, to limit the passenger seating configuration, excluding pilot seats, to nine seats or less is not
  applicable to Australian aeroplanes certificated under Section 101.22
  of Civil Aviation Orders.

In the type certificate for the Cessna 208B reference is given to the UK CAA approval for more than 11 seats.

New Zealand

New Zealand allows the 208 to be operated with 14 seats.

  In New Zealand the Model 208 Caravan has been approved for operation
  in the fourteen seat configuration in accordance with the provisions
  of the Fourteen Place Seating Supplement to the Model 208 Pilot’s
  Operating handbook. (A similar Supplement is included in the Flight
  Manual for the 208B.) The 208 aircraft was “accepted on the basis of
  compliance with FAR23 excluding the wording of FAR 23.1(a); ‘that have
  a passenger seating configuration, excluding pilot seats, of nine
  seats or less’.”

South Africa

The type certification document from New Zealand mentions that at the time of first approval (1985) Cessna stated:

  Australia, UK, South Africa, Norway, Sweden, Kenya and Columbia had
  all accepted the Cessna 208 with more than nine passenger seats.

Interestingly in February 2014 the CAA of South Africa (SACAA) denied that the 208 was ever approved for operation with more than 11 seats in South Africa. Operators using the Cessna 208 with more than 11 seats found themselves operating the aircraft illegally suddenly.

Quickly a Supplemental Type Certificate (STC) was approved in June 2014 which allows operation with 14 seats again.


How should I interpret this TAF involving TEMPO and BECMG blocks? with the reference in the TAF below , I was looking for the VIS at 0500 UTC and I was little bit confused because  of the " TEMPO "

And the TAF was

LHBP TAF (FT)140400Z 141206 34006KT 9999 BKNO45
TEMPO 1215 VRB10G2OKT 7000 SHRA SCT033CB BKNO40
FM1700 CAVOK
BECMG 2022 VRBO1KT 5000 BR NSC
BECMG 2201 1200 BCFG BR SCT002
BECMG 0104 0600 FG OVC001
TEMPO 0406 0150 FG VV001

According to the TAF at 0104Z VIS would be 600M, then we can see TEMPO at 0406 with 150 M VIS, so what VIS can we expect?  Can we say it is 600M with possibility to be 150 M? Or we can say directly it is 150M?

TEMPO means that there were be fluctuations in the weather in the time period specified, lasting as long as 50% of the time range specified. TEMPO 0406 0150 FG VV001 means that in the period between 04:00 and 06:00 UTC the visibility will at some point go down to 150 in heavy fog, and it could last up to an hour in total.

One thing I would point out is that the time range for the TAF ends at 06:00, so its very likely the fog will last longer than that.


What is the main difference between 'continental fuel injection system' and 'Bendix RSA fuel injection system'? While I'm studying Aircraft Engine system, I learned that there are two dominant kinds of fuel injection system : 'continental fuel injection system' and 'Bendix RSA fuel injection system'

I tried to find the main difference between those systems, and all I found out was that the former one injects fuel before the each cylinders, in the manifold(with nozzles connected to manifold valve assembly), and the latter one injects fuel directly into the each cylinders(and the nozzles are connected to a fuel divider). But I'm not sure this is true or not, since there are no part that explains the exact difference between them.

Could anyone let me know about this?

First of all, both of these systems are continuous flow fuel injection systems, therefore they do not inject fuel directly into the cylinders. Since the fuel is flowing continuously from the injector nozzles, the spray is directed into the induction system just before the intake valve. That way, the fuel will only enter the cylinder when the intake air charge is drawn into the cylinder as the intake valve opens. Both systems have a throttle body to house the throttle valve, and a fuel servo/regulator to meter the correct amount of fuel and control the air to fuel mixture. The primary difference is how the fuel is metered. The RSA system (originally manufactured by Bendix Corp.) is found on Lycoming engines and is the next evolution after the pressure injection carburetor. The RSA system uses a combination of differential air pressure and differential fuel pressure to regulate and meter the fuel flow. The two sources of air are the low pressure air in the throat of the venturi and the high pressure air from the "ram air" entering the throttle body. At wide open throttle, these two forces have the greatest differential pressure, so they move a diaphragm and a valve in the fuel regulator to increase the fuel flow and pressure. The Teledyne Continental Motors fuel injection system does not use air metering force. This system relies only on differential fuel pressure.


Aircraft Identification: What single-engine, T-tail, commuter aircraft has a single prop but sounds like a jet? My morning walk takes me past Hillsboro Airport, Portland, Oregon (HIO), and today I saw a rather strange plane landing.  It was a small commuter-size plane (6 passenger windows on each side), with a single surprisingly large propeller on the nose.  While landing it sounded much more like a jet than a prop.  The tail was "T" shaped and I thought I saw a jet exhaust at the back of the fuselage.

Was I imagining this, or does such a craft exist?

Sorry I didn't get a picture.

Sounds like a Pilatus PC-12 to me.

image source: Wikipedia, photographer: Chris Finney


Why don't B747s start takeoffs with full throttle? Why does the 747 start takeoff with partial power and increase to full throttle later down the runway, when the A380 for example starts on full?

Source

This is not the same question as:

Is it possible that derated thrust takeoffs are safer than normal takeoffs?
Why don't airliners use full throttle on takeoff?

The other answers are spot on, but I'd like to address one part, which is the "later down the runway." It is by no means "later."

(YouTube)

In the frame grab above of a 747-400 (taken at 1:12), the captain had already called out "takeoff thrust," the TO/GA system had set the pre-programmed thrust setting, and the 747 wasn't even at the piano keys. (Auditory cues can be misleading to passengers or air side spotters.)

Typically, a low thrust setting is set to make sure all the engines are responding in the same way, and more importantly, will have uniform application of thrust thereafter. This can be done with (standing takeoff) or without the brakes on,$^1$ or during a rolling takeoff. Then it is TO/GA time. (In tail-wind conditions, the procedure may vary.)

Here's another video by JustPlanes from inside the cockpit. Again TO/GA was pressed while the plane was at a crawling pace far from being anywhere later down the runway.

$^1$ Boeing 747-400 FCTM § 3.4


Should the route be changed if the GPS RAIM prediction fails? Do i have to change the route if the GPS RAIM prediction has one or more outages along my route?

The answer to this question will probably depend on the equipment involved and type of route being flown; as asked, the question is open ended, and there are several types of operations where the answer is a definite "no" (i.e. you do not need to adjust your route), while in other situations, that answer might change.

If you are flying on Victor airways using VOR receivers, then the answer is certainly "no".  You aren't navigating with GPS, so you don't care about the RAIM.

If you are flying in RNP-3 or RNP-10 airspace (i.e. the required navigation performance is 3 NM or 10 NM -- so your INS can drift that far before you need to do something different) with an INS or multiple INS's, then you probably don't care about the RAIM... your INS's won't drift that far in several hours, and the RAIM should be back to acceptable limits well before then. (Maybe there are exceptions to this; I'm not aware of any.)

If you are flying an approach where GPS is your primary navigation, then YES, you absolutely do need to change your plans if the RAIM fails.  Break off that approach, go somewhere where the RAIM is good, use a conventional navaid for the approach, whatever the best option is for you.

I'm not aware of any enroute operations where RAIM is a factor; what I'm flying has dual INS's and the FMC can update its position off of not only the GPS but also from conventional (DME/DME, or VOR/DME) navaids, and we don't worry about the RAIM enroute, even when flying Q routes where GPS is required.  (Maybe that's a hole in our OpSpec, I dunno.)  We do look at it when flying an RNAV approach.


Is it possible to estimate the location of aerodynamic center without experimental moment data? In airfoils, the aerodynamic center is usually found close to the quarter chord point, but for quick calculations, we assume it lies on the quarter chord.

What I am looking for, is if there is any way to find a rough estimate as to where the aerodynamic center is actually located on a tested airfoil - given only lift and drag data.

The tested airfoil is mounted on the sting on its quarter-chord point, which sits on top of a force transducer. The angle of attack is varied throughout the test.

The pressure distribution $c_p$ on an airfoil is necessary to determine the aerodynamic center of an airfoil. From the pressure distribution you can obtain all three coefficients $c_l,c_d,c_m$ (well, for accurate $c_d$ you better have a rake for high $L/D$ airfoils). Having only the first two, as in your case, is not enough. Simply because there are many $c_p$ distributions that will give the same $c_l$, $c_d$ forces and different $c_m$ forces. These airfoils will also have a different aerodynamic center. Thus, the answer is no. If you don't have means of measuring the moment, couldn't you just vary the mounting position of the airfoil to estimate moments and do your job?

However, in case you want only a rough (experimental) $c_m$ estimate you can relate your airfoil basic characteristics ($c_l,c_d$, zero lift angle, camber and thickness distributions etc.) to similar airfoils found in this classic reference and interpolate.


Can a Boeing 747 take off fully loaded on 3 engines? Recently a Boeing 747 aborted a take off while still on the ground due to the failure of one engine.

Can a Boeing 747 take off fully loaded on 3 engines?

The short answer as detailed to some degree in previous answers and comments is that a 747 can takeoff if the engine fails after the V1 speed is reached but not if the failure occurs before reaching V1. Unfortunately, in my opinion, the owner of one of the answers has deleted his answer, which while perhaps imperfect did provide useful information, and perhaps as important will remove the comments.
It's best to understand the V1 speed within the context of a balanced field takeoff. See this Wikipedia article for a full explanation. The first two paragraphs are:

A balanced field takeoff is a condition where the accelerate-stop distance required (ASDR) is equal to the takeoff distance required (TODR) for the aircraft weight, engine thrust, aircraft configuration and runway condition.1 For a given aircraft weight, engine thrust, aircraft configuration, and runway condition, the shortest runway length that complies with safety regulations is the balanced field length.
The rejected takeoff initial actions speed V1, or critical engine-failure recognition speed (Vcef),is the fastest speed at which the pilot must take the first actions to reject the takeoff (RTO). At speeds below V1 the aircraft may be brought to a halt before the end of the runway. At V1 the pilot must continue the takeoff even if an emergency is recognized.

Let's translate this into a practical situation using a 747-200 with old steam gauges. Prior to engine start five plastic bugs would be positioned around the rim of the airspeed indicator: the first at V1, the second at VR, the third at V2, and the last two at speeds not relevant to our discussion. We're rushing down the runway at takeoff power and all goes well. When we reach V1, the PNF says "V1" and the PF takes his hand off the thrust levers (he had them there in case of an abort). When we reach VR, the PNF says "rotate" and the PF brings the yoke back briskly but smoothly to a pre-determined nose attitude (usually 12 or 13 degrees). When the landing gear is off the runway, you'll hear the gear down lock retract unlocking the gear up lever. When the PNF sees a positive climb rate on the vertical speed, he'll say "positive rate", the PF will call "gear up", the PNF will move the gear lever to up. When the airplane reaches V2 the PNF will say "V2".
The important thing to remember here is that if there had been an engine failure after V1, the only difference would have been that the first person to know which engine had failed would have called "engine failure #1" say. On the old 3-crew airplanes, that would usually be the f.e. Even if the engine was burning, no action would be taken until after V2, and probably not until after you had a clean airplane.
Just as a matter of information, here are some V speeds for a 747-200 with P&W JT9D-7Q engines for a Flaps 10 takeoff at 840,000 lbs:

V1 168 kts
VR 181 kts
V2 189 kts

Now for an abort. An abort below 80 kts is no big deal. Between there and 100 kts gets more interesting. Above 100 kts it is not to be taken lightly, and an abort at say, 150 kts, is a bonafide emergency. A friend of mine had to do one of those, and he blew all of the 16 tires that had brakes. In my view, if an engine failure occurs within a few knots either way of V1, you're better off flying.
To quote from an accident report in which I was involved in the investigation:

The bang and the loss of power occurred around V1 speed. Two seconds after the bang, all four engines were brought back to idle, and braking action was initiated. The thrust reversers were not deployed.
The aircraft came to a stop 300 m after the end of runway 20, above a railroad embankment. The aircraft was severely damaged; it broke in three parts.


What is the use of saw-teeth present on the nacelle outlets of modern turbofans? I've noticed that there are saw-teeth on modern jet engines such as the GEnx and the Rolls Royce Trent 1000. What is their purpose?

These "saw-teeth" or "chevrons" or even "acoustic liners", are there to help reduce noise generated from the operation of the engine.

As hot air from the inner core of the engine mixes with the other, cooler air, it generates noise. These "saw-teeth" are there to help smooth that mixing, thereby generating less noise which is the result of turbulence. These are seen on the Boeing 747-8 (as seen in your picture) and the Boeing 787.

The reduction of sound generated means that less noise insulation is needed for use in the fuselage of the airplane. Less insulation means less weight. Less-weight equals less fuel burn, which means that chevrons are great for passengers, and economics.

There's only one difference from your picture. As much as we would like them to blow kisses to everyone, that's not what they are there for. :)


Why does Boeing 737 use 2 Inertial Reference Systems (IRS) and GPS? According to this website the Boeing 737 aircraft use 2 IRS and 2 GPS: IRS L & IRS R. Why? Apparently they are totally independent of each other.

Could somebody explain a little bit why they need 2 separate GPS and 2 separate IRS?

Follow-up question: this same website states: "POS INIT is used to enter the aircraft position into the IRS's for alignment". What is meant by "alignment"?

Could somebody explain a little bit why they need 2 separate GPS and 2 separate IRS?

So that if one fails, the other can still be used to complete the flight.

Airbus even have 3.

  What is meant by "alignment"?

Initialization of the system and solving the "heading problem" through a magnetometer. But this is a different question.


Is a VFR flight following request implied when talking to tower and advising them of your intended airport? If I am at a towered airport in class delta airspace and I'm departing VFR and tell the ground where I want to go, is it implied to the controller that I'm requesting VFR flight following?

Let's say I'm at the Chandler Municipal airport (KCHD), and I'm headed to the Scottsdale airport, which is in another class delta, and I probably need to transit the Phoenix bravo airspace.

I call Chandler Tower up and say:

"Skyhawk 283JS with information sierra, FBO, north departure to Scottsdale airport"

Will the tower controller coordinate flight following for me and assign a squawk based on this request? Or do I need to specifically request "VFR flight following" if I want it?

It is not. You must explicitly add

  Requesting VFR Flight Following

Depending on the airport in question the tower may simply tell you to contact approach once in the air to request flight following. Other towers may set it up for you.

The notation of your destination is extraneous. When departing you generally tell the tower you direction of departure not your destination.

Flight flowing is also not an implied bravo clearance, you will need to request that once in the air. If you are taking off from a towered field you can ask for a handoff when requesting your clearance, this may help facilitate your clearance request as well as your flight following request.


Do ducted fans have a future in forward flight aircraft? Can they be made more efficient than open rotors? I'm fascinated by how ducted fans have the ability to be more efficient than open propellers of equal diameter in vertical flight through the use of tight tolerances, lightweight duct material, proper duct lip shape, and other factors. However, when learning that these benefits don't translate over into horizontal flight due to the duct's induced drag and pitching moment, I'm wondering if we'll ever see ducted fans in future aircraft.

I'm aware of the NASA ducted fan manned-aircraft project that failed in the 60's, but today I found out about AgustaWestland's Project Zero and noticed that they tilt the ducts and include fixed wings to provide sufficient lift. How would an aircraft like this compare efficiency-wise to something like a similarly sized  two rotor helicopter?

AgustaWestland Project Zero

Fan shrouds are a fix for a problem that can normally be designed around in other, more efficient ways. They do reduce tip loses, but usually the tip loses are smaller than the weight and drag penalty of the shroud.

The fundamentals of prop/fan/rotor design is that thrust is proportional to the increased momentum of the air flow, but the power required to get that thrust is proportional to the added kinetic energy i.e. the ''square'' of the speed increase.

Therefore small, highly loaded fans will always be inefficient compared to a traditional helicopter rotor. The fact that they suffer from large tip losses only makes things worse.

So no, we won't see lots more ducts on future aircraft - except that jets already use ducts because the size of their fans are limited by ground clearance and keeping the fan blades subsonic.


What does the balance ball actually indicate? Given answers and comments from a previous question, I realize that I need to clarify what the ball actually measure. I think it does not measure side slip but sideways acceleration, but I'm not quite sure.

Let's say, I put a ball in a roller coaster. Whatever the maneuver performed, there can't be side slip (no wind, the roller coaster is basically a train). Those maneuver include:

boat turns (the ball should be on the external side of the turn)
straight horizontal trajectories (the ball should be centered)
straight trajectory with a bank angle (the ball should be on the lower side)
a simple roll

How does this differ from in flight situations? Given what the ball actually measures, what makes it reliable to be used as a side slip indicator?

bonus question: if I take a long aircraft (e.g. a AN-225) and put a ball in several places in the aircraft, will all those indicator concur in a not coordinated turn?

1. Preamble

The ball reacts to the body force (or acceleration), with the exact same working principle as a bubble level. In airplane frame, the force is expressed as:

$$Y+mg\cos{\theta}\sin{\phi}=m(\dot{v}+ru-pw)$$

where $Y$ is all external side forces minus gravitational component, $m$ is airplane mass, $g$ is gravitational acceleration, $\theta$ is pitch angle, $\phi$ is roll angle, $\begin{bmatrix}u & v & w\end{bmatrix}^T$ is the inertial velocity in vehicle frame, $\begin{bmatrix}p & q & r\end{bmatrix}^T$ is the angular velocity in vehicle frame.

First, as any accelerometer, the ball does not react to gravity. Second, and this is a preference in bookkeeping, you can consider the accelerometer (or the ball) to only react to the external forces (i.e. $Y$), or only react to the inertial forces minus gravity (i.e. the right side of the equation minus the gravitational component).

2. In Flight

Taking thrust out of the question, then in flight, the only thing that can contribute to $Y$ is aerodynamic forces. What's the largest source of lateral force in air? Sideslip. There you have the relation between ball measurement and sideslip angle measurement. If you're unconvinced, read the sub-sections below.

2.1 Symmetric Thrust and Airframe

For symmetric thrust and airframe, the only yaw moment sources come from aerodynamics, and the largest contributors are sideslip and rudder (ailerons and spoilers also contribute due to differential drag, but the effects are even smaller).

Using the B737 model in AVL at Mach 0, flap 0 and AOA 0 for a rough idea, -5 deg rudder generates about 4.4deg of sideslip (nose left), at which point their yaw moments cancel each other out. However, the total $C_y$ is 0.055 to the right.

Comparing the stability/control derivatives (per rad), $C_{y_\beta}$ is -1.2, whereas $C_{y_{\delta_r}}$ is 0.44, which means that at the aforementioned conditions, the sideslip is overpowering the rudder by 140%, in terms of side force.

2.2 Asymmetric Thrust

In the case of one engine inoperative (OEI), we need to overcome the yaw moment from thrust asymmetry via rudder.

For wings level, there is side force from rudder that must be compensated. This can be accomplished by generating more sideslip into the live engine (which means more rudder deflection is needed than to overcome the thrust yaw moment). At steady-state, the net side force is zero, the ball is centered, but there is steady non-zero sideslip.

If we allow the wings to bank toward the live engine, a portion of gravity can be used to compensate for the side force from rudder, which means that less sideslip induced side force is required to maintain steady-state (therefore less rudder required). However, since the total side force minus gravity ($Y$) is non-zero, the ball is skewed to the live engine.

In either case, with thrust asymmetry, the relationship between sideslip and side force are "broken".

3. On Ground

On ground, any point of contact with the ground provides additional sources to $Y$. This is why tilting the bubble level with your hand makes it not measure level: it's not that the level is responding to gravity, but rather that it's responding to the normal forces exacted by your hand.

For an airplane, the source is obviously coming from the landing gear contact. At high speed taxi on a straight runway, with crosswind, the sideslip creates aerodynamic side force. The landing gear resists lateral motion via an opposite side force (however, you'd need to deflect nose wheel or rudder to resist yaw moment). At steady-state, the yaw string would measure sideslip, but the net side force is zero, so the ball would measure nothing.

Things are different when it's a circular runway. Because the airplane needs to track a curvature, the combined lateral forces must provide the centripetal forces necessary to maintain the track curvature. Therefore, the ball would react to the equivalent centrifugal force.

4. Sensor Positioning

Thus far, we've been assuming that the ball is placed exactly at the airplane CG. If the sensor is offset, then it will also react to the angular rates. That's why large airplanes need to calibrate the sensor measurements to the assumed CG position.

To answer your last question, unless the airplane is tracking linear motion, placing the sensor at different locations will give you different readings.


What's the functional difference between PAPI and VASI? PAPI and VASI seem to be very similar in the the information they provide - i.e. are you on the glide slope or off it. Is there a functional difference between the two? If there is a difference, and one is superior to the other, is there a construction cost savings where an airport might chose one over the other?

A PAPI and a VASI are very similar in the the information they provide. The only functional differences between the VASI and PAPI is that the VASI has the red over the white, the PAPI the white actually goes to the right of the red, and the PAPI offers higher precision (or more glideslopes depending how you look at it a larger airliner with a high cockpit may elect to fly a slightly higher glidepath). The concept is the same though.

A VASI looks like this:

Usage:

As the saying goes,

  Red over White, you're alright. (on glidepath)

  Red over Red, you're dead. (too low)

  White over White, you're out-of-sight (too high)

A PAPI like this:

A regular VASI only offers one glide slope and is designed for an aircraft where the cockpit isn't so high up. However, there is a such thing as two-light PAPI, and a three-bar VASI. So either of them can really be tailored to fit the costs and types of aircraft flying to that airport.

In the case of a four-bar PAPI it is higher precision. Since the PAPI systems uses a narrower beam of light you must fly the glide path more precisely than the VASI to stay on the beam. The PAPI, with its extra lights, forewarns you when you are drifting from the desired glide path.

(source: airportlightingcompany.com)

So one red light would indicate slightly above glide slope, two and two would indicate the normal glide slope, and three red lights would indicate slightly below the glide slope on a 4-bar PAPI. A Three bar VASI works in similar fashion except there are only two glide paths with two reds being the lower, two whites the higher.


If operating an ultralight with private pilot certificate, which rules apply? If a holder of a private, commercial, or ATP pilot certificate operates an ultralight aircraft; and that aircraft is also equipped with the radios and transponders required by an airspace for GA aircraft, can this flight operate under standard VFR rules as a GA aircraft rather than operating under ultralight rules? (ie. Using non-towered airports which are marked "ultralights prohibited" in the chart supplement, and controlled airspace airports.)
All of the regulation of airspace that I can find is focused on either the pilot's certificate and rating, or the aircraft equipment, rather than the aircraft category and class. That is a slow "experimental" light-sport STOL bush plane (which could be as slow as an ultralight), a C172, or a King Air 250 are all equally allowed into class E, D, C, or B airports as long as they have the required electronics and a PIC with a private pilot certificate or above.
I ask mainly because I would like to use an ultralight for commuting, and the places I commute are airports of the above nature. (local street traffic is terrible, and I need STOL capability for my home field. Less than 700ft to clear a 50ft obstacle.)

If the aircraft is not registered, it can only be operated under part 103.
FAR 103.1 states that an ultralight may not "have any U.S. or foreign airworthiness certificate".  So a registered aircraft could not be operated under Part 103.
Your question mentioned transponders.  Bear in mind that FAR 91.1(e) exempts ultralight vehicles from all of Part 91.  Therefore, if operating under Part 103, there is no particular airspace that would become available if a transponder were added to the ultralight, that would not be available otherwise, unless a particular ATC facility chose to grant the "prior authorization" required for Part 103 operations in certain controlled airspace, specifically on that basis.  This seems unlikely.  In fact, it is probably safe to assume that the FAA would attempt to prohibit a transponder from being added to an aircraft operating under Part 103, although it's not clear what regulation this would be based on.
Related:
In the United States, are ultralights legally considered aircraft?
Would FAR 91.227, or any other regulation, forbid use of ADS-B-out in an unregistered ultralight?


Why is there a cutout in the pilot seat (looking as if it had separate "legs")? Why is there a gap in the seat (between the legs)?
What function does it have?

I can't speak to all aircraft, but on the 727-100 and 747-100/200 aircraft I flew, the seat cutout accommodated the strap on 5-point seat belt systems that went down between your legs. See

https://pitstopusa.com/c-134853-safety-equipment-seat-belts-harnesses-cam-lock-restraint-systems-5-point-camlock-restraints.html.

I don't recall for certain whether the control yoke could be brought all the way back into the cutout, but I don't think it could. I may be misremembering though.

As I remember, the camlock into which the other 4 straps (left and right across the seat and left and right shoulders) was permanently attached to the strap going down between the legs. On sitting in the seat, you reached down and pulled that strap up with the camlock on the end and then put the other 4 straps into their slots.

I greatly disliked the shoulder restraints, so once we reached cruise climb, I would rotate the camlock while holding the left and right seats straps in. This would release the shoulder straps.


Why is there a plateau in helicopter H/V diagrams? The "dead-man's curve" in a typical helicopter height/velocity (H/V) diagram is commonly referenced to indicate that "towering flight" is dangerous and avoided in general practice.  (Simon explained, "The Avoid curve [outlines] the combinations of height and speed in which test pilots (i.e., the best) have demonstrated that a safe landing is possible if the engine quits.")

But H/V diagrams also have second envelope that is marked for avoidance.

I don't know if this area in the lower right has an ominous name: If not perhaps we should call it the "dead-man's plateau?"

But why is it considered unsafe to fly at extremely low altitudes at indicated airpseeds above about 50 knots?

In a comment on this in the answer above Simon says, "At that speed, if the engine quits, the nose will pitch down and you will be on the ground, with no control and high speed, before you know what's happened."

Can someone elaborate on the dynamics of this?  Why would the nose pitch down abruptly if the engine quits?  If that's such a reliable effect would it not be trivial and worthwhile to have a torque-driven spring that bears on the cyclic, so if torque suddenly changes then the cyclic is just as suddenly nudged backwards?

In any case, one is left wondering if the full answer isn't more nuanced: The most striking characteristic of the dead-man's plateau is that it appears to be the height at which one enters ground effect.  Is there some other aerodynamic phenomenon at play in high-speed ground effect flight?

As speed increases, most helicopters pitch up.  This is because the lift generated on the side of the retreating blade gets progressively less than the lift generated on the advancing blade side.

Due to precession, the effect of this is felt 90 degrees later so instead of rolling to the left (or right, depending on which way the blades rotate) because of the dissymmetry of lift, the tail drops, therefore pitching the nose up.  Whether this happens on a particular helicopter, and by how much, depends largely on the pitch stabilisers.  However, helicopters are naturally unstable in pitch.  You cannot take your hand of the  cyclic and maintain a constant attitude, absent any autopilot or other automatic assistance.

As the helicopter accelerates, the pilot subconciously counteracts this by applying foward cyclic pressure.  The higher the speed, the more forward pressure is needed to maintain altitude and the helicopter flies nose down.  You fly a helicopter by "sight picture" to such an extent, that to accelerate, you pitch the nose down to give you the "65 kt picture", or the "100 kt picture", allow the aircraft to accelerate to the desired speed, then trim.  The nose is pitched down a lot at 100 kts compared to say 50.

When the engine quits, assuming it's an instantaneous failure, there is nothing to stop that forward pressure forcing the nose down and at such low heights and high speed, losing 18 feet of height before the pilot reacts and pulls back to flare would be easy.  Even if they react really quickly and flare without losing much more than 5 or 10 feet, there is a very real risk that the tail will strike the ground and at those high speeds, that will result in a really bad crash.

Let's assume that everything goes right. There is no time at that height to lower the collective and raise it again.  You will also have a lot less than a second to flare so will lose very little forward speed.  In the best case, you are going to land at 50 kts or higher with the collective in your armpit and the rotors already stalled, if not stopped altogether, and this is at best a bad crash, quite possibly fatal.

The most important thing to remember is that the shaded areas represent the flight regimes where test pilots, with instant reactions since they initiate the manoeuvre, cannot demonstrate a safe landing with no damage.  This is at the edges of the shaded areas and once they get to the point of saying "one more foot, and we would not have had a successful landing", they stop exploring the envelope and draw the curve in the POH.  To add a safety margin, the tests are done at max weight.  Even so, the wise pilot will give those areas a wide berth whenever possible.

Why isn't there some automatic device to pull the cyclic back?  Because you do not do this if the engine quits when in a hover or up to about 10 kts at low height.  In the avoid area you ask about, it would need to pull, then push to level the skids again in the blink of an eye.  It's different when hovering at 1,000 ft and different again if doing 90 kts at 1,000 ft. And that's before we add all the variables - pressure altitude, temperature, wind strength and direction.

To deal with all of this, you would need a very clever system loaded with sensors.  Most people call such systems "pilots".

I would rather just avoid the shaded areas.  It's no big deal.


Why is more oxygen required at higher altitudes? Referring to a chapter from Aircraft Maintenance And Repair

Normal air contains approximately
21 percent oxygen, and this provides adequate oxygen for
the human body at lower altitudes. At 34 000 ft [10 363 m]
altitude, a person must be breathing 100 percent oxygen
to absorb the same amount of oxygen as when breathing
air at sea level.>

Why is it required for us breathe 100% oxygen to absorb same 21 percent of oxygen we would breathe at ground/ lower altitudes?

This question is best answered on https://biology.stackexchange.com, but in short it is the partial pressure that counts. This is (pressure in atmospheres) * (percentage).
At 0.5 atm (18 kfeet) you need twice the amount of oxygen in the air (aka 40%) for it to have the same effect on you. Above 38.5 kfeet the pressure is 0.2 atm, so even 100% oxygen will only provide 20% partial pressure of oxygen, which is the same as normal air at sea level


How can I calculate a pitch/power table? I want to make a pitch and power table for C172s based on calculation, just like I attached above.

I picked up this table on internet, but I'm not sure where it comes from.

Do you have any ideas how to get these values?

I got the answer from cessna company, as below.

The pitch/power table you have provided is not a product of Textron Aviation and has been developed outside of our flight testing and engineering. We have no formula available for calculating required pitch attitudes, The table shown appears to be developed by a flight school based on actual flight test observations.
In general terms, pitch relates to angle of attack. Angle of attack required for certain climb and descent rates are dependent on variables such as gross weight, C.G. location and indicated airspeed. In relation to the quote “pitch + power = performance”, a more accurate approach for developing a quick reference chart assuming the aircraft gross weight and C.G. remains constant is to match indicated airspeed with power settings. Pitch + power can approximate an airspeed, but more accurately power + airspeed = pitch. Flying an aircraft “by the numbers” relies on power settings and airspeeds, which consequently will produce a certain pitch attitude. Conversely, to facilitate a desired climb or descent rate we set power and approximate a pitch attitude to arrive at the desired airspeed.
The interrelation between pitch and airspeed is for the most part interchangeable, but most accurate is thinking of pitch attitude being a consequential product of power and airspeed in the context of normal flight maneuvers.

Well, nothing new here. But I found that there are no exact formula to deal with power and pitch table. I'll try to collect actual data.
Thank you guys.


Why do certain airlines give names to their aircraft? That is the case for aircraft operated by e.g. KLM. Some aircraft are named after birds, some after cities. Is that common for other airlines as well or something that only KLM does?

The practice of naming aircraft probably comes from the days of the flying boat, and the naval tradition of naming ships - the Pan Am Clippers had many named aircraft, and Pan Am kept up the tradition into the Jet Age. Other airlines of the period had similar naming practices (I'm not sure who started it, but Pan Am's fleet was well known for it).

As a marketing tool telling folks they're flying on "Clipper Emerald Isle from New York to Dublin" may have been more attractive to passengers than "Pan Am Flight 12345" or N880PA. Particularly before the commoditization of air travel, when flying was still a new and novel form of transportation, having a connection back to familiar "sailing" metaphors may have helped get passengers on board and could help differentiate your service from another airline.

Modern airlines don't seem to push their aircraft naming as much as historic carriers did, but as SentryRaven noted there are a few airlines that still name their ships - in fact Lufthansa paints their plane names onto the fuselage, though I'm not sure if they announce them to passengers.
A skilled marketing department could build a brand around ship names, but I'm not aware of any airline doing so today.


On a flight with short stops, do you terminate flight following at each stop? On a cross-country trip, is it normal to terminate FF at each stop and reacquire it (potentially just a few minutes later) for the next leg, or would ATC prefer that you advise them it'll be a short stop and maybe let you keep the code to reduce their hassle later?

As @RonBeyer notes in the comments Flight Following will drop you when you land. Generally (also as Ron notes) they will ask you to call the "field in sight". It really depends on where you are and what kind of air space you are in. Where I fly in the Northeast they typically drop you when you have the field in sight but its hard to stray to far from a heavily controlled area if you are flying between DC and Boston but it may be different elsewhere.

Keep in mind that you will need to get off the frequency so you can make your CTAF announcements anyway. It may be a good idea to keep the controller as a listen only channel on COM2 if you are equipped for such in your aircraft.

Assigning you a code is not really a hassle for them so you don't need to worry. In a busy airspace ATC may want you out so they can handle IFR traffic. Remember flight following is "load dependent" so you might not always get it and you can be dropped out at any time.

When on your student XC's its always a good idea to preface one of your initial calls with "N123AB Student Pilot requesting flight following". ATC is there to help you and noting you are a student pilot may help you so they don't expect professional pilot level flying and radio chatter from you.


Which manufacturer produced this fan blade? I acquired a fan blade a few years back, but have not had any luck finding out who manufactured it or what engine/aircraft it may have come from.
The only data I can find on the blade is as follows:

4922T12P01
99207 6018730P02
KGA 65444
GR.IN.
15.620

65444 is hand engraved again in larger size above the data listed, which I assume is the serial number. The blade is about 15" from tip to root. I am curious about the root itself, as I have not seen other blades with a mount like this one. If anyone can help out it would be greatly appreciated.

Images can be seen in full size by clicking on them

GE Aviation

Clue 1. Parts designed at the Lynn MA plant have part numbers of the form xxxxTxxPxx, where x is a digit. 4922T12P01 fits that pattern.

The gr.in is another clue. That refers to a weight that would be used in balancing the fan. GE uses units of gr.in. I'm fairly sure that Pratt uses oz.in, snecma uses gr.cm. I'm not sure what RR uses.

But the definitive piece of information is 99207. That is a CAGE code. 99207 is registered to GE Aviation's lynn plant. I looked it up here http://www.govcagecodes.com/


Is a full traffic pattern required when there is no traffic at an untowered airport? If there seems to be very little traffic at an untowered airport, and no one's replied to any of your radio calls, is it acceptable to just fly a straight-in approach to the runway, or should you still fly the full traffic pattern to final? It just seems like it would be a waste of time and fuel when it's not really necessary. Is there anything wrong with doing so?

See AC 90-66A - RECOMMENDED ‘STANDARD TRAFFIC  PATTERNS AND PRACTICES FOR AERONAUTICAL OPERATIONS AT AIRPORTS WITHOUT OPERATING CONTROL TOWERS  for information about uncontrolled airport traffic patterns.

It includes the following which says that while the FAA recommends using the full pattern, it is not required:

  7. GENERAL OPERATING PRACTICES.

  a. Use of standard traffic patterns for all ‘aircraft  and CTAF procedures by radio-equipped aircraft  are
  recommended at all airports without operating  control towers.
  However, it is recognized that other  traffic patterns may already be
  in common use  at some airports or that special circumstances or
  conditions exist that may prevent use of the standard  traffic pattern

And then:

  e. The FAA encourages pilots to use the standard  traffic pattern.
  However, for those pilots who choose  to execute a straight-in
  approach, maneuvering for  and execution of the approach should be
  completed  so as not to disrupt the flow of arriving and  departing
  traffic. Therefore, pilots operating in the  traffic pattern should be
  alert at all times to  aircraft executing straight-in approaches.

  f. Pilots who wish to conduct instrument  approaches should be
  particularly alert for other aircraft in the pattern SO as to avoid
  interrupting  the flow of traffic. Position reports on the CTAF
  should include distance and direction from the  airport, as well as
  the pilot’s intentions upon completion of the approach


What is the stick at the bottom of the tail on a ATR-72? During my last flight I observed the ATR-72 has a stick protruding from the bottom of the fuselage, near the back of the airplane.

See the bottom of the fuselage in this picture, slightly to the left of the rear door.

I assume it impedes take off and must be removed before flight.

What is it?

It is a tail stand, also called as pogo stick and is used in the aircraft during loading/unloading. It is basically a stick, which is carried around in the aircraft and attached to the rear fuselage using a pin during loading/unloading operations, as can be seen in the image below.

Air Dolomiti ATR 72-212A (I-ADLS) - Removeable tail stand installed at the rear of the aircraft when it is parked on the ground. In case of weight imbalance, this prevents the aircraft from resting on its tail. By User:Mattes - Own work, Public Domain, Link

It is found in other aircraft like Saab-Scania SF340B etc.

You're right that it must be removed before takeoff to prevent potential structural damage. However, there have been instances where aircraft have taken off with them. There have been other issues too:

  First of all, there have been previous incidents where the ground crew have just tossed the tail stand into the aft compartment and not replaced it into the storage bracket. As a result, the tail stand has gotten jammed into the control cables for the tail surfaces which run through that compartment. ... . The second reason is that being less visible, the built in tail stand would occasionally be left connected to the aircraft on departure creating the potential for structural damage.

Because of this, external metal stools are used in some cases. Of course, the aircraft can be loaded/unloaded without the tail stand by loading the aircraft in appropriate sequence.


Does laser eye surgery prevent me from getting an EASA pilot licence? I am a masters student in Germany and I am very much interested in pilot training. I had a laser eye surgery (LASIK) 3 years ago. I heard that people who got it are not eligible as a pilot. Is this true for a private licence too?

LASIK is a type of refractive eye surgery and according to EASA's medical standards, you can be considered "fit" to fly after surgery if several conditions are met. The conditions depend on the class of medical; private pilots usually have a class 2 medical.

For class 1:

  (1)   After refractive surgery,  a fit assessment may be considered,
  provided that:
  (i)    pre-operative refraction was not greater than
  +5 dioptres;
  (ii)  post-operative stability of refraction has been achieved (less than 0.75  dioptres variation diurnally);
  (iii) examination of the eye shows no post-operative complications;
  (iv)  glare sensitivity is within normal standards;
  (v)   mesopic contrast
  sensitivity is not impaired;
  (vi)   review is undertaken by an eye
  specialist.

For class 2 (private pilot) and LAPL:

  After refractive surgery a  fit assessment may be considered provided
  that there is  stability of refraction, there are no postoperative
  complications and no increase in  glare sensitivity.

The LBA also has an FAQ on vision issues but it doesn't mention LASIK. It does say, however, that you need an optician to examine you if there are any questions about your vision that an aviation examiner can't determine himself (nicht durch den flugmedizinischen Sachverständigen durchgeführt werden können). I assume that means that if there's any doubt about your eyes, you'll need to have an additional eye exam.


Do aircraft need special modifications for polar routes? Does an aircraft need special modification for polar routes?

There are several considerations for flying polar routes, but no special modifications are necessarily needed.  Navigation is different, as Lat/Lon (specifically longitude) converge to become meaningless close to poles, so aircraft traditionally use a grid navigation system.  Aircrew should also be aware of the difference between magnetic and true north, as the magnetic "North Pole" is different than the geographical North Pole.

You should also understand your aircraft's temperature boundaries.  If you fly through the arctic in the depth of winter, you should ensure that all of your aircraft components are suitable for the temperature.  Usually, this isn't an issue - and if it was, you can always descend a bit to find "warmer" air.

Otherwise, air provides lift in the polar regions just like in the equatorial regions, and Bernoulli keeps your aircraft afloat!


How much extra drag does an external HF antenna incur? As seen in the picture, some older planes have external HF antennas that run from the fuselage to the tail.  Have any studies found the wire to be a significant source of drag or is the difference negligible compared to moving an entire plane through the air?

As this film shows with brilliant simpliciy, the drag of a round wire is almost 10 times the drag of the same thickness streamlined shape.

Biplanes use streamline rod for flying and landing wires because of this.  There is enough flying/landing wire on a biplane for it to make a huge difference.

On a long antenna wire however, there really isn't a practical way to streamline it, and even if you did, to keep the streamline contour properly oriented, so you just live with the drag penalty of the wire.

It also helps that the sharply "swept" angle of the wire in the picture to the airflow means the profile presented to the airstream is more of an oval shape than circular, so the drag of the swept wire will be somewhat less than a wire presented to the airstream at 90 degrees.

So in the case of the 737, the wire itself is probably pretty minor factor overall, but I wouldn't be surprised if the wire costs a couple of knots of cruise speed at a given power setting.


Is there any way to relieve the Pilot in Command? Is there any way to relieve the Pilot in Command besides hijacking and incapacitation?

This question comes from a comment by rackandboneman, who says:

  And whose authority is sufficient to make an active pilot in command a pilot out of command?

I gave a joking response, but it got me thinking: are there any ways to remove a PIC from command without that PIC's consent other than hijacking or incapacation, either in the United States or worldwide?

The regulatory bodies are reluctant in defining a regulation for that. Because there are first officers who do not hold an Airline Transport Pilot License. The airlines would need to add an extra flight member for that rare situation.

Instead, it's up to each airline's SOP when it comes to Crew Resource Management. There are various assertiveness training models, of which are PACE, and CUS.

Probe-Alert-Challenge-Emergency
Concerned-Uncomfortable-Safety

Facing battery depletion following an electrical failure, here's an example for what the last step of PACE could have been like on October 11, 1983:

  Captain, if you don't immediately reverse course and get back to night VFR conditions, I must take over control of the airplane. I cannot allow you to subject the passengers to such an unnecessary and high risk of certain death. Under these conditions, it is my duty and responsibility to relieve you of your command. (To Intervene or Not to Intervene? The Co-pilot's Catch 22)

Or, it can be much shorter when there's no time, such as asserting, "I have control," and pressing the TO/GA to initiate a go-around, for example.

Some airlines use only two steps, i.e., "I've mentioned my concern once, this will be the second and final time, else I'm taking command."


How to carry out a CFD simulation for determining the stability derivatives of an aeroplane? I want to create a 3D model of an aircraft to determine the stability derivatives by using a computational fluid dynamics (CFD) simulation. I tried to google for tutorials that explain how it is possible to carry out a CFD simulation for determining the stability derivatives of an aeroplane but was not successful. I would be glad if someone could give some resources that explain the procedure. It would be great if the CFD software would be ANSYS Fluent.

Make a list of the derivatives you want to determine. All of them will be derivations of some force or moment with respect to some parameter or control setting. Now set up your CFD such that you get lift, side force and drag as well as pitching, rolling and yawing moment relative to the center of gravity.

Next, make those forces and moments dimensionless. Forces are divided by a reference area (projection of the wing area in most cases) and the dynamic pressure (speed squared times air density divided by 2). Moments are in addition divided by a reference length (span or semi-span for rolling and yawing moment, mean wing chord for pitching moment). The results are called coefficients. Record those coefficients for a baseline configuration (say, level flight at cruise speed).

Now make a small change in the parameter (angle of attack or sideslip, speed, air density, pitch-, roll- or yaw-rate) or control setting (elevator, rudder or aileron angle, flap setting, power setting) and record the coefficients again. Only one change at a time and leave all others at their baseline position! The desired derivative is simply the gradient of the coefficient over the gradient of the parameter, as in
$$c_{M\alpha} = \frac{c_{M1}-c_{M0}}{\alpha_1-\alpha_0}$$
with 0 denoting your baseline figures and 1 the changed ones. Use radians for all angles. The rotation rates you should make dimensionless by dividing the value by the flight speed and multiplying it with the respective reference length. And another thing: The really correct reference length for the pitching moment and -rate is the mean aerodynamic chord which is the integral of chord squared over span, divided by wing area.


Do helicopters have automatic tail rotor compensation for anti-spin? Helicopter pilots need to push on the pedals constantly to compensate for the main rotor torque, so that the helicopter does not start an unintended spin. But it would be annoying to indefinetly put pressure on the pedal. Do helicopters  have an autopilot that automatically keeps them stable ?

Autopilots control the flight path, they usually concern themselves with the travel of the centre of gravity of the aircraft. Stabilising the aircraft is more the job of the human pilot. In a helicopter that is indeed not an easy job - larger helicopters have a mechanical mixer that helps the human do that, a set of lever arms that input extra tail rotor as collective is applied, for some automatic compensation of the increased torque of the main rotor.

Having to indefinitely put pressure on a flight control is an annoying issue for fixed wing pilots as well, that is why they can be trimmed. Stick and pedal forces can be trimmed away, so that the neutral point of the control becomes the point of zero force: once the control is trimmed, you can take your hands or feet off of it and it stays there.

In fixed wing aircraft, trim is usually adjusted with a flick switch on the handle. Flick it sideways and the roll control spring neutral point moves, flick it forwards and the pitch spring neutral point adjusts. Helicopters have such a switch as well, and that works well for fine control in cruise. But in the hover there is a lot of swishing action of all flying controls, and the beep trim switch is just too slow to follow this. Spring forces that are normally helpful, are now a hindrance.

That is why helicopters in addition have a trim on/off button: when selected, all feel forces cancel and the stick or pedal is very light, only a bit of friction and damping. What happens is that the feel forces neutral point automatically follows the stick position. Once the helicopter is stable, the trim forces can be selected ON again, and hands and feel can be removed - although I believe this is never a good idea in a helicopter.


How is Turbojet defined by the FAA? During my commercial ground school today, we were asked if turbojet and turboprop aircraft are defined differently by the FAA. While I know the answer is yes, I don't know where in Title 14 the answer can be found. I've searched multiple resources for over two hours.
Thanks!

The FAA does not define the terms turboprop and turbojet in the FARs.  These terms are defined in the Pilots Handbook of Aeronautical Knowledge.

Turbine engine. An aircraft engine which consists of an air compressor, a combustion section, and a turbine. Thrust is produced by increasing the velocity of the air flowing
through the engine.

Turbocharger. An air compressor driven by exhaust gases, which increases the pressure of the air going into the engine through the carburetor or fuel injection system.

Turbofan engine. A fanlike turbojet engine designed to create additional thrust by diverting a secondary airflow around the combustion chamber.

Turbojet engine. A turbine engine which produces its thrust entirely by accelerating the air through the engine.

Turboprop engine. A turbine engine which drives a propeller through a reduction gearing arrangement. Most of the energy in the exhaust gases is converted into torque, rather than using its acceleration to drive the aircraft.


Do ultralights need to have EPA-compliant engines in the USA and Canada? Do ultralights need to have EPA-compliant engines in:

The USA?
Canada?

Just wondering if you could use a hobby type 2 stroke engine for a twin engine Lazair type ultralight.  I don't think they are EPA compliant.

I know some people use them.  Just wondering if it's actually legal?

No such thing as EPA compliance on General Aviation engines or ultralight engines for that matter.  You buy a piston engine from Continental or Lycoming, it has no pollution controls of any kind. It's like it's 1960.  There just aren't enough of them to make any real impact, so they get a pass.

Pretty much anything goes for a Part 103 Ultralight in the US or what is called a "Basic Ultralight" in Canada.  Whatever suits you.


How does a taildragger take off? Does it rotate? All the planes I've ever seen taking off (big airliners) first lift the small front wheel from the ground, then rotate and ultimately lift up.

If the small wheel is on the tail instead, in which sequence are the wheels lifted from the ground? Lifting the tail wheel first would pitch the plane down, so the sequence is most likely different.

There are three different schools of thought there, and one can be selected based on the capabilities and characteristics of the tailwheel aircraft you are flying.

Fly the tail off the ground:  After achieving full power during the start of the takeoff roll, apply forward stick pressure until the tail lifts off and the aircraft assumes a level attitude on the main gear, then hold that pitch attitude for the rest of the takeoff roll.  This technique can be done in most underpowered taildraggers and is useful for short field takeoffs and landings as it minimizes parasite drag and flat plate area during the takeoff roll.  It will require a healthy bootful of right rudder to counter the change in P-Factor as well as gyroscopic precession from the propeller.

Let the tail fly off the ground:  After applying full power with full aft stick deflection, neutralize pitch input to the stick and continue the takeoff roll.  As speed builds, the tail will lift off the ground naturally.  This is the recommended technique when flying high performance tailwheel planes like WWII fighters, etc.  where good rudder authority is needed to counter P-Factor changes and precession.

3-point takeoff:  Apply full power and hold full aft stick as well as additional right rudder to counter for P-Factor.  As speed builds in the takeoff roll, gradually ease up on stick pressure but hold just enough to keep the tailwheel on the runway.  As the airplane lifts off the runway care must be taken to quickly adjust elevator pressure to hold a gradual climb and prevent rapid pitch up and stall.
I once flew an MX2 with an oversized prop offering only about two inches of ground clearance resting on the mains in level attitude.  We were taught to only do 3-point takeoffs and landings and specifically warned not to attempt anything else to prevent a propstrike.


Who runs the Air Navigation System (air traffic control) in Canada? Who runs the Air Traffic Control system in Canada? Is it the government?

No. Unlike the United States where the Federal Aviation Administration (FAA) is both the operator and regulator of the air navigation system (ANS), these roles are separated in Canada and performed by two different parties. They are:

The regulator: Tranport Canada - Government of Canada
The operator: NAV CANADA

The Government of Canada passed the Civil Air Navigation Services Commercialization Act of 1996, which effectively sold the ANS to a newly-formed corporation, "NAV CANADA" for the price of $1.5 billion dollars. Since 1996, Transport Canada's role has changed to regulation and enforcement; they introduce, amend, revoke, and enforce the Canadian Aviation Regulations.

NAV CANADA become the sole operator of the civil ANS and is a private company whose revenues come from aviation customers and technology sales, not Government of Canada.

NAV CANADA operates the civil ANS using 7 Area Control Centres, 41 Control Towers, 56 Flight Service Stations, and 8 Flight Information Centres; military aerodromes and terminal control areas remained the responsibility of the Department of National Defence.


If an aircraft flies straight ahead, does it follow an orthodrome/great circle? I understand that an orthodrome (line on a great circle) is the line with the shortest distance between two points on a sphere.

If an aircraft flies straight ahead, i.e. there is no wind, the rudder is not actuated and the aircraft is parallel w.r.t. the surface of the earth underneath it, will it follow an orthodrome/great circle?

I also understand that a loxodrome is the line that one follows when keeping a constant heading. This is the point where I'm confused, because wouldn't that mean that when flying straight ahead/along an orthodrome, the heading/bearing would constantly change? In other words, does this mean that one needs to turn in order to keep a constant heading?

EDIT: My question is not "which line does one follow when keeping a constant heading" (a loxodrome, I know that) but rather "what line does one follow when flying straight ahead (in the hypothetical case of no wind and no control inputs)?"

There isn't a perfect answer to this, but effectively yes.

Anything that moved in a completely straight line would of course leave the curved  surface of the Earth and go off in to space. And realistically no vehicle of any kind could perform the (lack of) manouvers described above with no control changes.

To perform the best approximation of 'straight flight' while staying on the surface of the Earth would mean deviating from the true straight line only in a direction perpendicular to the Earth's surface. This in turn means staying in the plane defined by containing the vector of direction of initial motion and also the centre of the Earth. The intersection of the Earth's surface with this plane - i.e. the path the craft would actually follow- would be the great circle. And in answer to the last part, yes, when flying a great circle the heading constantly changes.

EDIT: This does, of course, assume a reference frame relative to the Earth, as pointed out in comments..


If I have a float plane, can I land on any body of water? What are the rules with regards to landing a float plane on a body of water?  Can I land anywhere (non-emergency, obviously) that would also accommodate the take-off?  If not, how do I determine which bodies of water would allow it and which would not?

It really depends on the state, though you can't land in National Parks (the National Park Service regulates that, not the FAA).  The FAA doesn't care where you land it, though if you ball it up due to poor choice of landing area then they'll have something to say.

Some states don't really care where you land (like Oregon), others don't let you land anywhere (like New Jersey).  You should contact your state and get the regulations from them.