39
votes
Accepted
Why are airplanes parked at the gate with max rudder deflection?
The control surfaces of airliners are not connected to the pilots' control via cables; they are operated by a hydraulic pump. When the engines are shut down, there is no hydraulic pressure in the ...
- 39.6k
33
votes
What is this open panel at the rear of this airplane?
It is the Auxiliary Power Unit (APU) inlet door.
Image from Boeing Aero Magazine
- 99.9k
30
votes
Why do T- tail airplanes have a shorter vertical stabilizer?
Two reasons:
T-tail design is often imposed on designs with twin engines mounted at the aft fuselage. This means they have a small moment arm in the yaw direction, the vertical tail is dimensioned to ...
- 61.1k
26
votes
Accepted
Why don't commercial aircraft use all-movable tail surfaces like my RC plane?
What is better and easier for small-scale models is not necessarily better for larger aircraft.
First, you can't say that the fixed part "does nothing". The tail is primarily a stabiliser; without it,...
- 8,993
23
votes
Why don't airliner vertical tails extend to the very aft of the fuselage?
Spin resistance and area ruling
Locating the vertical a bit ahead of the horizontal tail brings it out of the probable wake of the horizontal at high angle of attack, so it still is effective in ...
- 228k
22
votes
Has there ever been a sideways H-tail on an airplane?
Most of the initial aircraft made by Wright brothers had the twin horizontal stabilizer setting. However, the elevators in these cases were set in the front, rather than back, as is the norm now.
By ...
- 99.9k
21
votes
Accepted
Has there ever been a sideways H-tail on an airplane?
The double decker horizontal tail was a popular choice for large biplanes, even into the 1930s. Below is a picture of the Zeppelin Staaken R VI giant airplane and below it a Handley-Page H.P.42 ...
- 228k
18
votes
Accepted
What is this object on an MD-11?
As was said in the comments above, it is the support structure for the engine as seen in this drawing:
- 37.3k
18
votes
Does tailless means no tail at all?
Tailless means no horizontal tail, but a vertical tail is still allowed. Examples are the Convair F-102 or Convair B-58.
Convair B-58 Hustler (picture source)
Compare this to a flying wing: Here ...
- 228k
16
votes
Accepted
Why is the horizontal stabilizer root interface designed this way?
It is a seal- to prevent entry of air into the stabilizer mounting area. For aircraft with trimmable horizontal stabilizers (THS), there is an opening to the rear of the aft bulkhead to allow for the ...
- 99.9k
16
votes
Accepted
Why are aircraft designed so that the wing stalls before the tail?
You are missing the weight force. The wing should stall first because then it will produce less lift and the weight will make the aircraft pitch down.
In attached flow, the lift from wing and tail is ...
- 228k
16
votes
Accepted
What is the function of this fixed protrusion on the tail?
That is almost certainly a navigation antenna.
From the E190 AOM (Airplane Operations Manual):
You can see the VOR2/LOC2 antenna rather more clearly in this photo:
(The VOR1/LOC1 and VOR3 ...
- 3,751
16
votes
Why are fighter jets equipped with dorsal fin?
There are two features that you may be referring to.
A) Is an antenna that is shaped to provide low drag. Not all F16 have this.
B) The true dorsal "fin":
increases structural strength
decreases ...
- 11.3k
15
votes
Accepted
Why do the C-141 and C-5 have T-tails?
It comes down to a matter of philosophy. Or, if you are less generous, it’s a matter of fashion. Note that the Russian equivalent to the C-141, the Il-76, uses a T-tail, too, while the An-124 uses a ...
- 228k
15
votes
Accepted
What is this little strake on Cessna 182 vertical tail?
It's one half of a VOR receiver antenna. There will be a corresponding element on the otherside of the tail.
The complete unit looks like this:
Source
Disclaimer: I have no affiliation with the the ...
- 3,606
14
votes
Why are airplanes parked at the gate with max rudder deflection?
I have no experience on Boeing or Airbus airplanes but the most likely cause would be gust locks installed on the aircraft.
Some aircraft, like a C-172, have a pin that locks the aileron and ...
- 12.2k
14
votes
Accepted
How exactly do the Beechcraft 1900's stabilons work?
This Flight Safety Training Manual describes them as improving "deep stall" characteristics and C of G range.
The stabilons are fixed surfaces that add effective stabilizer area to improve ...
- 125k
14
votes
Accepted
Why don't airliner vertical tails extend to the very aft of the fuselage?
The three main duties of a vertical (as well as horizontal) stabiliser are:
to trim;
to control;
and to provide with stability the airplane.
the root of the vertical tail doesn't extend right to the ...
- 8,302
13
votes
Accepted
Why is the DC10/MD11/TriStar vertical stabilizer noticeably smaller than other contemporary aircraft?
Two characteristics drive vertical tail size in airliners:
Critical engine out: Here the tail needs to compensate the yawing moment of the live engine on one wing.
Yaw damping: This is aided by a yaw ...
- 228k
13
votes
Accepted
How do tailless aircraft yaw?
Technically the B-2 bomber has rudders, they are "drag rudders" (or split rudder) and are located on the outer portion of the wing:
Source: Quora
The rudders open in a clamshell ...
- 36k
12
votes
Accepted
What are these unsymmetrical parts at the tail of the Tupolev TU-144?
The four parts you're referring to contain the actuation mechanism for the rudder, similar to the wing pods that contain the flap actuation mechanism.
The reason they are not arranged symmetrically ...
- 99.9k
12
votes
Why do T- tail airplanes have a shorter vertical stabilizer?
Raymer gives the following answer:
The 'T-Tail' is also widely used. A T-tail is inherently heavier than
a conventional tail because the vertical tail must be strengthened to
support the horizontal ...
- 121
12
votes
Accepted
Why is the empennage design of this Lockheed 1049E so complicated?
Complicated is a matter of opinion and I wont address that specifically since its somewhat subjective. But the core of the question is "why did the L-1049E have 3 tails" which is a legitimate question ...
- 100k
10
votes
Why aren't there V-tail airliners?
Controllability and redundancy. Airliners are certified according CFR 14 Part 25, which specifies that upon engine fail the aircraft must still be able to fly and climb: it must have more than one ...
- 61.1k
10
votes
Why do the C-141 and C-5 have T-tails?
High wing military aircraft (c141 and c5 both are) use T tails for multiple reasons.
to prevent rocks and debris from damaging the tail when landing off airport
to keep tails out of the engine thrust ...
- 18.8k
9
votes
Accepted
Is there a formula to calculate how big a ventral fin should be?
There is no single formula - the number of factors to consider are too numerous and the load cases are too diverse. Here is an incomplete list:
Directional stability: Depending on fuselage size and ...
- 228k
8
votes
What are the benefits of a non-orthogonal (scissor) tail-rotor?
Image source
The tail rotor of the Apache consists of two 2-bladed teetering rotors, referred to as scissor rotors. This unusual configuration was first implemented by Hughes Helicopters in the late ...
- 61.1k
8
votes
Has there ever been a sideways H-tail on an airplane?
There is quite a famous example of this!
but other than the Wright Flyer, I don't know of any.
My layman conjecture as to why this is not more common is that the tail only needs to be large enough ...
- 578
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