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Pilot Creates Delay To Avoid Wake Turbulence

Pilot Creates Delay To Avoid Wake Turbulence

Old Jun 12, 21, 4:53 am
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Pilot Creates Delay To Avoid Wake Turbulence

What would happen if, with planes lined up to take off, one pilot determines that air traffic control did not allow enough time for the previous departure wake turbulence to dissipate and he intentionally dilly dallies on his own takeoff, perhaps filling the 15 or so seconds with a little banter on the subject with ATC.
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Old Jun 12, 21, 9:06 am
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I'd give the pilot a prize. He acts from experience. Having once experienced severe wake turbulence upon landing (where the plane was tilting sharply from side to side, wingtips pointed toward the runway over the SFO runway) where the pilot had to promptly get us back to altitude, I will not question the pilot's action.
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Old Jun 12, 21, 10:51 am
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safety first … the captain has the final say
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Old Jun 12, 21, 11:25 am
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The FAA's Aeronautical Information Manual (AIM) offers the following guidance.

Pilots may request additional separation (i.e., 2 minutes instead of 4 or 5 miles) for wake turbulence avoidance. This request should be made as soon as practical on ground control and at least before taxiing onto the runway.
NOTE-
14 CFR Section 91.3(a) states: “The pilot-in-command of an aircraft is directly responsible for and is the final authority as to the operation of that aircraft.”
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Old Jun 12, 21, 10:38 pm
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Originally Posted by AllanJ View Post
What would happen if, with planes lined up to take off, one pilot determines that air traffic control did not allow enough time for the previous departure wake turbulence to dissipate and he intentionally dilly dallies on his own takeoff, perhaps filling the 15 or so seconds with a little banter on the subject with ATC.
Of course this may create a situation where an arriving aircraft is forced to go around while the bantering pilot dilly dallies on the runway in use.

As the AIM states in the above post, the extra delay should be taken prior to entering the runway.
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Old Jun 13, 21, 9:50 pm
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Originally Posted by Tanic View Post
Of course this may create a situation where an arriving aircraft is forced to go around while the bantering pilot dilly dallies on the runway in use.

As the AIM states in the above post, the extra delay should be taken prior to entering the runway.
While that is all well and good in theory, the delaying pilot may not be 100 percent aware of what particular aircraft is involved at that time.
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Old Jun 14, 21, 11:09 am
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Thanks.


Oh, by the way, the pilot in question will not be aware of much. All he knows is that the previous plane took off and, after a short pause, ATC gave him the go ahead. In this hypothetical scenario the pilot judges that by the time he would get into position on the runway and should take off himself, the previous plane would not be far enough away. So, still at the front of the takeoff queue, the pilot places his request to ATC for more time.
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Old Jun 14, 21, 10:03 pm
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Originally Posted by AllanJ View Post
Thanks.


Oh, by the way, the pilot in question will not be aware of much. All he knows is that the previous plane took off and, after a short pause, ATC gave him the go ahead. In this hypothetical scenario the pilot judges that by the time he would get into position on the runway and should take off himself, the previous plane would not be far enough away. So, still at the front of the takeoff queue, the pilot places his request to ATC for more time.
But oh, by the way, the pilot in question would know the aircraft was, for instance, a 757, and s/he has had previous wake turbulence experience above and beyond the normal, etc.
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Old Jun 14, 21, 10:30 pm
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Originally Posted by AllanJ View Post
Oh, by the way, the pilot in question will not be aware of much. All he knows is that the previous plane took off and, after a short pause, ATC gave him the go ahead. In this hypothetical scenario the pilot judges that by the time he would get into position on the runway and should take off himself, the previous plane would not be far enough away. So, still at the front of the takeoff queue, the pilot places his request to ATC for more time.
When wake turbulence is involved, takeoff clearances are predicated on weight class of preceding aircraft (small/large/heavy/super) and the succeeding aircraft. It can be measured in whole minutes 2/3/4 or radar distance, but would not be a short pause. The takeoff clearance cannot be issued until the prescribed interval in time or distance has passed.

As always, the pilot in command is the final authority to operate the aircraft, but could be required to leave the runway for other traffic.
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Old Jun 15, 21, 9:43 am
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Originally Posted by AllanJ View Post
What would happen if, with planes lined up to take off, one pilot determines that air traffic control did not allow enough time for the previous departure wake turbulence to dissipate and he intentionally dilly dallies on his own takeoff, perhaps filling the 15 or so seconds with a little banter on the subject with ATC.
Kudos to the pilots. They are required to observe and comply with wake turbulence separation requirements. Passengers arent.

Last edited by freshairborne; Jun 15, 21 at 9:49 am
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Old Jun 15, 21, 9:48 am
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Originally Posted by Tanic View Post
When wake turbulence is involved, takeoff clearances are predicated on weight class of preceding aircraft (small/large/heavy/super) and the succeeding aircraft. It can be measured in whole minutes 2/3/4 or radar distance, but would not be a short pause. The takeoff clearance cannot be issued until the prescribed interval in time or distance has passed.

As always, the pilot in command is the final authority to operate the aircraft, but could be required to leave the runway for other traffic.
TCAS is also used, in addition to visual observation, ATC clearances, and experience. All things that passengers are not generally aware of.
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Old Jun 15, 21, 11:59 am
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Originally Posted by Eastbay1K View Post
But oh, by the way, the pilot in question would know the aircraft was, for instance, a 757, and s/he has had previous wake turbulence experience above and beyond the normal, etc.
ATC usually gives us enough spacing, and that becomes the expectation. In some situations they don't, and we won't necessarily know that ahead of time. A lot depends on the conditions and our weight, which affects our ability to stay above the preceding aircraft's wake.
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Old Jun 15, 21, 2:54 pm
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This is mainly an issue with 757's, right? They aren't quite heavy, but they throw off a nasty wake...
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Old Jun 15, 21, 3:31 pm
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Originally Posted by pinniped View Post
This is mainly an issue with 757's, right? They aren't quite heavy, but they throw off a nasty wake...
The strength of the wake vortices is proportional the the aircraft's weight so heavier aircraft produce stronger weights. The 757's max weight fell below the "Heavy" category, but higher than other non-heavy aircraft. It was initially treated like any other Large aircraft, not a heavy, so tighter spacing following a 757 than following a Heavy. It had pretty strong wake as compared to other aircraft in the Large classification.

Another problem is the 757s excellent climb performance. It was able to climb more steeply than most of the aircraft hat might be following it which put those aircraft into its wake more often than would normally occur.
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Old Jun 20, 21, 12:18 pm
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Originally Posted by AllanJ View Post
ATC gave him the go ahead.
Once ATC gives the, "go ahead" obviously that means the pilot CAN go. Does anyone know how long he/she has to pause before they MUST go? Is it essentially expected that they immediately go once given clearance? Presumably, ATC is timing things and is expecting the pilot to be out of the way shortly.

I suppose it could be different if the same runway is being used for take-offs and landings whereas one used just for take-offs wouldn't be as critical.
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