Idle thrust reverser landings.
Brake wear was about 25% higher with REV Idle v Full Reverse, but brakes are cheaper to service than the cost of extra fuel burned + reverse maintenance.
"The importance of establishing the desired reverse thrust level as soon as possible after touchdown cannot be overemphasized. This minimizes brake temperatures and tire and brake wear and reduces stopping distance on very slippery runways.
The use of minimum reverse thrust as compared to maximum reverse thrust can double the brake energy requirements and result in brake temperatures much higher than normal."
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The problem with only using idle reverse after touchdown is that some aircraft such as the 737 will drop to ground idle of 23%N1 if after 4 seconds reverse has not been selected. If for some operational reason during the landing run, the pilot suddenly decides full reverse is needed, it can take up to 10 seconds before full reverse spools up from idle reverse. As the aircraft slows on the landing run, reverse becomes less effective as a braking medium, and the situation is made worse by the long spool up time from reverse idle.
The other factor to remember, especially on 30 minute turn around times that some LLC use, is that the brake temperatures can be much higher than normal if landing using idle reverse (see Boeing TCTM advice above).
That means the next take off after the 30 minute turn around will start with already hot brakes. Not good airmanship. In turn the already hot brakes could reduce the braking efficiency if a high speed rejected take off should subsequently occur. Plus possibility of brake fire after stopping due max brake energy exceeded.
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Cough: quite right, I agree. I was curious, as the comparison is all about costings, just what the overall cost analysis was of all the various combinations. Of course, the takeoff & landing performance on slippery runways would be compromised. So let's keep them on.
Idle REV and minimum turnarounds, as operated by some we love & hate, has always been a question. I wonder if those guys do brake cooling calculations Before & After every landing, or would it be too complicated, confusing, embarrassing etc.
Idle REV and minimum turnarounds, as operated by some we love & hate, has always been a question. I wonder if those guys do brake cooling calculations Before & After every landing, or would it be too complicated, confusing, embarrassing etc.
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When landing on a dry runway at normal landing gross weights, I rarely selected more than idle reverse thrust if my planned runway turnoff point was greater than 6000 ft from touchdown.
But hey, that's just me.
Some guys go to maximum reverse no matter how much runway they have remaining.
But hey, that's just me.
Some guys go to maximum reverse no matter how much runway they have remaining.
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Notwithstanding that, I tend to do landing perf. and brake cooling calculations anyway and I don't really get minimum turnaround times.
