What is Jet Wash

[F-22]

What is Jet wash I've heard about it but never really knew what it was???:confused:


Thanks..:)

[Cool_Hand]

Jet Wash is the spiralling horizontal column of air coming out the back of a turbine, making for a bumpy ride and a horrible presentation of air into your engine (hot and transonic in speed :eek:).

[PPRuNeUser0171]

Is that the same as wake turbulence then?!

Thanks,

--
Gary Williams

[Pilot Pete]

Wil

not quite, wake turbulence refers to the turbulent air left behind an aircraft and includes the turbulent air due to the wing tip vortices.......do a search on here for that if you want to know more about what causes them in detail, but basically the way the wing produces lift is by the aerofoil shape causing lower pressure above the wing and higher pressure below the wing which 'sucks' the wing upward, as a consequence of these differing pressures the higher pressure air naturally tries to mix into the lower pressure and thus 'escapes' from under the wing-tip around to above the wing. As the wing is moving forward at speed the resultant 'mixing' forms a tight spiral motion of air trailing from each wingtip (these can often be seen in moist air). These spirals are like mini-tornados and do not dissipate immediately, hence the need for a time gap between aircraft landing/taking off on the same runway (where they will pass pretty much through the same air) as this wake turbulence can be very dangerous for a following aircraft, especially if it is lighter than the preceding a/c.

PP

[basil fawlty]

The turbulent disturbance of the air due to an aircrafts flight through it is called wake turbulence or vortex wake.
Jet wash (or jet blast!) is the exhaust from the engine. Only a problem on the ground in the relatively close confines of the ramp/cul de sac. I have felt it several times while doing the walkround, a blast of warm air from an aircraft pushing back or turning opposite. Its effects can also be carried with a bit of wind too. Some confined stands have "dead" pushbacks, ( the sierras at LHR T4 spring to mind) i.e no start up until pushed back and towed forward, in order to prevent any possible damage to objects or persons from this jet wash.

[spekesoftly]

Excuse me, but are we confusing 'turbulent wake' with 'vortex wake' ?

A lorry, for example, travelling at some speed will produce 'turbulent wake', as it pushes its way through the air.

An aerofoil, as a consequence of generating lift as described, produces 'vortex wake' - the one to avoid when following another aircraft.

But please correct me if I'm mistaken.

[PaperTiger]

For a graphic illustration of jet blast, see:
http://www.aagsc.org/miscellaneous/Jetblast.mpeg
(978k mpeg)

[PPRuNeUser0171]

For a graphic illustration of jet blast, see:
http://www.aagsc.org/miscellaneous/Jetblast.mpeg
(978k mpeg)

Wow!!!!

I remember seeing the 777 documentary on the Discovery channel and it amazed me just how much power a single engine has.
Mind you I suppose we should not be surprised, after all the engine has to move an aircraft which weigh many tonnes.

--
Gary Williams.

[mono]

Nah!

Jet wash is like prop wash.

One you use to clean a jet, the other a propeller.

:D :D :D :D

[cormacshaw]

quote:
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For a graphic illustration of jet blast, see:
http://www.aagsc.org/miscellaneous/Jetblast.mpeg
(978k mpeg)
------------------------------------------------------------------------

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