100 votes
Accepted

Why isn't the Presidential 747 "Air Force One Heavy"?

FAA JO 7110.65 Section 4 Radio and Interphone Communications specifically states that the "heavy" designator should not be used: e. When in radio communications with “Air Force One” or “Air ...
aeroalias's user avatar
  • 100k
28 votes

Why isn't the Presidential 747 "Air Force One Heavy"?

The purpose of the "heavy" designator is create situational awareness because of its wake turbulence. There are also different separation requirements when following a heavy aircraft. Since all air ...
Steve Kuo's user avatar
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12 votes
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Does the wake from horizontal stabilizers merge with the wing wake?

Yes, when viewed from far enough away. Close up, both will have their own developing wake. The boundary layer leaving wing and tail will leave a speed discontinuity, and the downward moving wing wake ...
Peter Kämpf's user avatar
12 votes

How do aircraft refueling in-air deal with wake turbulence?

Like to see the fleet and crews talking here. I am a US Navy A7E pilot who flew in the Med aboard the USS Nimitz in the mid-1980's. I served as tanker pilot, and had my share of plugging behind an A6 ...
Aaron's user avatar
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11 votes
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Why there is no wake turbulence right after touch down or before rotation?

Well there may be vortex formation on the ground under certain conditions, but it doesn't stick around long enough to really be measured or cause trouble. Any time a wing is producing lift it will ...
voretaq7's user avatar
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11 votes

What is the safe separation for landing a Cessna-172 behind a commercial airline jet?

It depends on the size of the preceding aircraft. ICAO PANS-ATM-Doc 4444 Air Traffic Management has some values. 5.8.2 · Arriving aircraft 5.8.2.1 Except as provided for in 5.8.l.l a) and b), the ...
aeroalias's user avatar
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10 votes
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What is the minimum separation between two landing A380s?

In general, the heavier an aircraft is, the greater the wake it produces but, it is also less affected by the wake of other aircraft. In particular, an aircraft can always resist the wake turbulence ...
Simon's user avatar
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10 votes
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If a pilot's plane suddenly and unintentionally becomes inverted, what is the pilot's best course of action?

What you are describing is Unusual Attitude Recovery (UAR) techniques, which are a standard part of the training for every Private Pilot1 Here is a good description of just such an event. Almost all ...
abelenky's user avatar
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10 votes
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With a separation of 1000 feet, in flight is there any danger of severe wake turbulence?

Summary: 1000 ft vertical separation is not enough for wake turbulence from a heavier aircraft flying above to decay. The wake turbulence will however be significantly less strong by then. A lateral ...
Bianfable's user avatar
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7 votes
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What vertical separation is required in a holding stack to avoid wake turbulence?

The minimum vertical separation in a holding stack is no different from the minimal vertical separation used elsewhere. This is almost universally 1000 feet. In countries where Reduced Vertical ...
60levelchange's user avatar
6 votes

Are there areas to avoid while flying formation with a larger aircraft?

In higher altitude the wake turbulence moves downward behind the aircraft. So as the pilot of the lighter aircraft behind the bigger you should keep the same level at least. photo by: Steve Morris, ...
Timothy Truckle's user avatar
6 votes
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Wake turbulence: crossing under a final approach path VFR

Due to the nature of wake turbulence descending over time and weakening as time goes on, I would say that it's possible that you hit the wake of the 737, and just managed to avoid the A380's wake out ...
Jamie Le Bas's user avatar
6 votes

Why did the pilot in this EC135 crash change the throttle setting after encountering wake turbulence?

It's the second sentence on the first page of the report: He inadvertently rolled the throttles to manual, and never restabilized the engines or main rotor rpm. Supplemented by (the next sentence): ...
Ron Beyer's user avatar
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6 votes
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How does the wake behind a propeller blade affect the next blade if the airflow through the propeller should be clearing the wake?

Aerodynamic induction works like electric induction since both can be calculated by the same laws. Those laws say that the influence of a vortex will decrease with the inverse of the square of the ...
Peter Kämpf's user avatar
5 votes
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Could reduced-lift wingtips allow an airplane to generate less wake turbulence?

Lift already does taper off gradually towards the tips, even on rectangular wings without any washout. That effect becomes stronger with tapered wings, of course. The reason is the pressure ...
Peter Kämpf's user avatar
5 votes
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Why does wake turbulence seem to move upward on touchdown?

Actually, yes, it is "upside down" as compared to the respective wing-tip vortices. Your picture shows the vortices coming off of the horizontal stabilizer, which rotate in the opposite direction ...
Devil07's user avatar
  • 8,554
5 votes

Why there is no wake turbulence right after touch down or before rotation?

Wake turbulence is related to the amount of lift produced. This in turn is proportional to the angle of attack of the wing. Before take-off rotation the wing produces little lift, so the effect of ...
Peter Kämpf's user avatar
5 votes

How and why do wake vortices come together to form two tip vortices?

The picture in your question is an oversimplification. Maybe this photo of an MD-11 on a moist day will help to illustrate the point: I also think you should not call the wake vortices "tip vortices"....
Peter Kämpf's user avatar
5 votes
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Is wake turbulence dangerous to planes of the same size?

Yes, wake turbulence can be dangerous to planes of equal size. Not so much at cruise stage, but during takeoff and landing, yes. The reason for takeoff, initial climb and landing phase being ...
Jpe61's user avatar
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4 votes
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Are there areas to avoid while flying formation with a larger aircraft?

In case of air to air refueling, the 'receiver' (the aircraft being refueled) should be careful about not getting into the wake of the tanker, which is usually much larger and heavy. For example, the ...
aeroalias's user avatar
  • 100k
4 votes
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Why aren't departures separated by minimum distance rather than minimum time?

For the FAA(all my answers can be looked up, and expanded upon in FAA Order 7110.65W, Chapter 3 mainly, but I'll try to keep it short), most departures from the same runway use distance for separation....
slookabill's user avatar
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4 votes

Is turbulence behind an airliner less severe during cruise?

The glider in question was "in touch" with the tip vortex of the A320 only with it's tail, and very briefly: Picture from section 1.16.2 on page 24 of the Accident investigation report. The ...
Jpe61's user avatar
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4 votes
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Is turbulence behind an airliner less severe during cruise?

To answer the question directly: Yes, in cruise turbulence is less severe, but it is lowest when flying low and fast. We can actually calculate the downward component $v_z$ of the wake (which is a ...
Peter Kämpf's user avatar
3 votes
Accepted

Is propeller wake turbulence quantifiable based on operating conditions?

As a rule of thumb, use fully turbulent flow at the elevated speed of the propeller wake on all surfaces wetted by it. The speed increase will result in higher friction drag compared to the propeller-...
Peter Kämpf's user avatar
3 votes

What vertical separation is required in a holding stack to avoid wake turbulence?

The minimum separation in a holding stack is still 1.000ft. Given that wake turbulence vortices move with the wind direction, you would have to fly the holding pattern with a direct headwind or ...
SentryRaven's user avatar
  • 15.7k
3 votes

What vertical separation is required in a holding stack to avoid wake turbulence?

From some of the ATC feeds I've seen transcribed controllers seem to prefer 2000 feet separation. Which makes sense if you consider that airplanes aren't going to hold on the exact altitude (which ...
ratchet freak's user avatar
3 votes

would a dimpled heat shield reduce heat transfer during reentry?

Near as I know, the key to designing good re-entry vehicles or shielding is large flat plates, primarily because the design ensures the energy transfer from kinetic and potential energy of the craft ...
Romeo_4808N's user avatar
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