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100 votes
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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
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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

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
  • 4,318
12 votes
Accepted

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
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

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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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
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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
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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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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
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
  • 29.3k
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
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 are differences between vortex, swirl, eddies and wake?

Wake is the general term for air disturbed by a passing aircraft, as might be guessed from the word's nautical origins. Vortex (in aviation, usually a wingtip vortex) is a part of the wake that ...
Camille Goudeseune's user avatar
3 votes

What is the relationship between angle of attack and wake turbulence?

It is not the angle of attack - downwash intensity grows with lift squared and inversely to the squares of wingspan and speed. Please read this answer on how wake turbulence forms. Now let's look at ...
Peter Kämpf'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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2 votes
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would a dimpled heat shield reduce heat transfer during reentry?

Golfballs are dimpled because the resulting turbulent boundary layer can follow the contour of the ball much better. Subsonic turbulent boundary layers have more drag than laminar ones, but fast ...
Koyovis's user avatar
  • 61.8k
2 votes

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

You have to think of where pressure is lowest and where it is highest. The wing is forcing air downward along its entire span, creating a low pressure area above the wing and high pressure below it. ...
TomMcW's user avatar
  • 28.6k
2 votes

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

Dissimilar formation flying has numerous hazards, and not just with tankers A classic example was the tragic accident in 1992 of a T-34 trainer getting too close to an F-14 while attempting to ...
KorvinStarmast's user avatar

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