Help needed for tech questions
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Joined: Oct 2005
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From: Australia
Help needed for tech questions
Can anyone help with a few of these:
1)Does the core still produce forward thrust during reverse in high bypass turbofan? If it does roughly how much?
2) After a ME Abort do the brakes get hotter afterwards? I assume the wheel assembly and tires would certainly get hotter due to heat transferral but do the brakes start cooling straight away?
3) What are the chances of a brake fire after a ME abort? Is it any different for carbon/steel brakes?
4)After a ME Abort would it be normal to evac the pax using the emergency escape slides or do you risk too many injuries by doing this?
1)Does the core still produce forward thrust during reverse in high bypass turbofan? If it does roughly how much?
2) After a ME Abort do the brakes get hotter afterwards? I assume the wheel assembly and tires would certainly get hotter due to heat transferral but do the brakes start cooling straight away?
3) What are the chances of a brake fire after a ME abort? Is it any different for carbon/steel brakes?
4)After a ME Abort would it be normal to evac the pax using the emergency escape slides or do you risk too many injuries by doing this?
Joined: Dec 2000
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From: on the golf course (Covid permitting)
My thoughts:
(1) Yes, the hot core airstream is not normally reversed on modern high bypass engines, unlike the older JT8D-type. I would guess the residual thrust to be about 20% of that when the cold stream is also at forward idle.
(2) For sure the brakes get hotter after a RTO - much hotter, reaching peak temps about 15 minutes later. With the aircraft parked there is no significant airflow to dissipate the heat. Google for some certification RTO trials for video evidence - one of the most hazardous parts of the certification process.
(3) See the answer to 2 above. Brake fire very likely if close to MTOW and near V1.
(4) Evacuating pax via slides should always be carefully considered and not done lightly as injuries are virtually inevitable from a large aircraft. You would want to consider all available information from windows, other aircraft, atc, the cabin crew and the fire services time permitting. Ask yourself the question 'Will they be safe staying on board' If the answer if yes, then do not rush into an evacuation, but remain flexible should the circumstances change.
(1) Yes, the hot core airstream is not normally reversed on modern high bypass engines, unlike the older JT8D-type. I would guess the residual thrust to be about 20% of that when the cold stream is also at forward idle.
(2) For sure the brakes get hotter after a RTO - much hotter, reaching peak temps about 15 minutes later. With the aircraft parked there is no significant airflow to dissipate the heat. Google for some certification RTO trials for video evidence - one of the most hazardous parts of the certification process.
(3) See the answer to 2 above. Brake fire very likely if close to MTOW and near V1.
(4) Evacuating pax via slides should always be carefully considered and not done lightly as injuries are virtually inevitable from a large aircraft. You would want to consider all available information from windows, other aircraft, atc, the cabin crew and the fire services time permitting. Ask yourself the question 'Will they be safe staying on board' If the answer if yes, then do not rush into an evacuation, but remain flexible should the circumstances change.
Warning Toxic!
Disgusted of Tunbridge
Disgusted of Tunbridge
Joined: Jan 2005
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From: Hampshire, UK
The heat-producing event in the brakes ceases when stopped, so do the brakes 'get hotter'? We know the temperature rises for about 15 minutes, but this is just the heat already in the brakes spreading out through the wheels and increasing tyre temperature. So would it be correct to say the brakes don't get 'hotter'? It's just the heat produced in 90 seconds spreading. Academic point only.
Carbon/steel either don't get as hot, or handle the high temperature better (can't remember), so are likely to be better.
One never automatically starts an evacuation without a definite need: fire warning or damage or bomb threat. After an abort, one would wait for a positive need to manifest itself. You must assume on any evacuation, there will be several broken limbs and hospitalisations, therefore the alternative must be certainly and definitely worse.
Carbon/steel either don't get as hot, or handle the high temperature better (can't remember), so are likely to be better.
One never automatically starts an evacuation without a definite need: fire warning or damage or bomb threat. After an abort, one would wait for a positive need to manifest itself. You must assume on any evacuation, there will be several broken limbs and hospitalisations, therefore the alternative must be certainly and definitely worse.
