Jet stream encounters
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Jet stream encounters
On a jet stream encounter there can be three possibilities (ideally of course) where the aircraft is hit by:
1. headwind
2. tailwind
3. crosswind
Could anyone provide a brief explanation as to the proper counteractive techniques that are used in the above three circumstances?
If say an aircraft encounters a severe headwind that causes a massive airspeed gain should the pilot try to stay level and what is the risk of damage to the airframe and/or control surfaces depending on the pitch attitude?
I'd appreciate any comments from pro's.
MB
1. headwind
2. tailwind
3. crosswind
Could anyone provide a brief explanation as to the proper counteractive techniques that are used in the above three circumstances?
If say an aircraft encounters a severe headwind that causes a massive airspeed gain should the pilot try to stay level and what is the risk of damage to the airframe and/or control surfaces depending on the pitch attitude?
I'd appreciate any comments from pro's.
MB
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Large airspeed changes seldomly come without any warning at all. Usually you will experience some light turbulence from the boundary in advance.
To avoid any inconveniencies due to fast airspeed changes, the common recommended turbulence penetration speeds are somewhere around halfway between minimum clean and VMO/MMO, like for example M0.76/285kts.
This will provide you with a speed margin sufficient to cover most sudden lateral wind changes.
Any really serious exceptions will hopefully be published by SIGMET or PIREP.
To avoid any inconveniencies due to fast airspeed changes, the common recommended turbulence penetration speeds are somewhere around halfway between minimum clean and VMO/MMO, like for example M0.76/285kts.
This will provide you with a speed margin sufficient to cover most sudden lateral wind changes.
Any really serious exceptions will hopefully be published by SIGMET or PIREP.
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Thank you RC for your reply.
However, my question refers to those abrupt wind changes that cannot be anticipated either by pilots or by weather reporting stations. I'm talking about clear air turbulence (CAT).
I know there have been a number of incidents involving aircraft damage, injuries to pax and even fatalities.
What I'm interested in is how pilots handle such situations in terms of thrust control, control inputs, etc.
And how much attention is paid to this issue during flight simulator sessions?
MB
However, my question refers to those abrupt wind changes that cannot be anticipated either by pilots or by weather reporting stations. I'm talking about clear air turbulence (CAT).
I know there have been a number of incidents involving aircraft damage, injuries to pax and even fatalities.
What I'm interested in is how pilots handle such situations in terms of thrust control, control inputs, etc.
And how much attention is paid to this issue during flight simulator sessions?
MB
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I think you are confusing jetstreams with windshear. Jetstream winds don't change so suddenly, and the wind component change does not cause problems- however the turbulence usually associated with the component change can. Encounters with windshear tend to happen closer to the ground where flaps and undercarriage may be deployed and the aircraft may not be in a good position to climb away. On final aproach, they tend to be obvious- the aeroplane may be in a peculiar attitude with the thrust levers far forward or backwards, and speed may still be running away. It should be obvious something is wrong. A bad encounter can be unrecoverable. But, during an encounter with the speed increasing and the thrust levers almost closed, better not to over-react and close them completely- you know that suddenly it will all change and the speed will be falling, your engines will be at idle and slow to accelerate, and you may be very embarrassed. Best not to chase the speed too aggressively trying to increase or reduce for when it will all change. Sorry if this is a bit cryptic, but it is a very complicated area.
In plain old turbulence, you just fight to keep the speed approximately right without overdoing thrust changes. Like the windshear feature, you know if it is increasing now,it will soon be decreasing- so don't get caught with slowly responding engines at the wrong speed.
In plain old turbulence, you just fight to keep the speed approximately right without overdoing thrust changes. Like the windshear feature, you know if it is increasing now,it will soon be decreasing- so don't get caught with slowly responding engines at the wrong speed.
Last edited by Notso Fantastic; 17th Jan 2003 at 18:46.
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CAT is mostly, but not necessarily, found on the cold side and in the area of narrow bends of a jet stream. You might ride a jet without the slightest shake but all the same encounter CAT in almost calm wind conditions.
The most important action after flying the aircraft is to try and get out of the turbulent area (climb/descend), unless its obviously temporal. Speed control is essential when penetrating turbulent conditions for two reasons:
To cover possible wind shear (keep speed away from Vmo or Mmo)
to expose the airframe to as little stress as possible
But CAT doesn't have to include rapid changes in wind component. You can get it with changes of wind direction as low as 10° and no change in wind speed at all...
Its danger is in the first place the stress it exerts on the airframe and the cleaning costs for the cabin afterwards
The most important action after flying the aircraft is to try and get out of the turbulent area (climb/descend), unless its obviously temporal. Speed control is essential when penetrating turbulent conditions for two reasons:
To cover possible wind shear (keep speed away from Vmo or Mmo)
to expose the airframe to as little stress as possible
But CAT doesn't have to include rapid changes in wind component. You can get it with changes of wind direction as low as 10° and no change in wind speed at all...
Its danger is in the first place the stress it exerts on the airframe and the cleaning costs for the cabin afterwards
