Idle thrust reverser landings.
Thread Starter
Idle thrust reverser landings.
Hopefully there's some of you in the know...
At airlines with idle thrust reverser landing policies, do you see a higher than expected increase in brake wear after its implementation?
I recognize few will have these answers, but a lot of diverse aviation backgrounds are present here, perhaps even some bean counters.
At airlines with idle thrust reverser landing policies, do you see a higher than expected increase in brake wear after its implementation?
I recognize few will have these answers, but a lot of diverse aviation backgrounds are present here, perhaps even some bean counters.
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Of course....
I understand the cost of brake wear/ ovehaul, as a result of increased braking is considered less than the increase in fuel and engine wear due to increased engine thrust used during reverse thrust.....
Economics....
I understand the cost of brake wear/ ovehaul, as a result of increased braking is considered less than the increase in fuel and engine wear due to increased engine thrust used during reverse thrust.....
Economics....
At airlines with idle thrust reverser landing policies, do you see a higher than expected increase in brake wear after its implementation?
the brake wear will be just about what one should expect when you use them harder
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Hi West Coast,
NASA conducted a survey in mid 90s; http://ntrs.nasa.gov/archive/nasa/ca...9950014289.pdf
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.
NASA conducted a survey in mid 90s; http://ntrs.nasa.gov/archive/nasa/ca...9950014289.pdf
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.
Back during the initial development of the 777 (and shortly after the Lauda 767 crash when a reverser deployed in-flight) I semi-seriously asked the question of why didn't we just get rid of thrust reversers (at least at that time, we didn't even get any credit for them under FAA regulations).
One of the discussion points was that using reversers saved over $100/landing in brake wear and maintenance.
Sounds like a classic case of 'pay me now, or pay me later'
One of the discussion points was that using reversers saved over $100/landing in brake wear and maintenance.
Sounds like a classic case of 'pay me now, or pay me later'
Thread Starter
Thanks to the few who took the time to read the question prior to hitting the reply button. I fully expect an increase, what I asked is if it was above what was expected. Laws of unintended consequences is what I'm trying determine from other companies experiences.
Golden and TD, thanks, certainly something to consider.
Golden and TD, thanks, certainly something to consider.
The unintended consequence is that it becomes normal to the crew and passmgers only to use idle reverse ,and the selection of max and the associated noise suddenly becomes quite unusual. In the A321 max reverse seems to be full of sound and fury signifying nothing in the braking produced, but that is probably because the autobrakes are looking at the total decelleration being produced not that of a single retardation device.
Only half a speed-brake
lompaseo: the only one to read the question 
.
WS I wonder how someone actually does measure brake wear and compare it before / after such policy is implemented (*). At the same time, many a task force / project group would certainly agree there is a brake wear increase, but the distinction between causality and confirmation bias is very hard to make. For sure, one who expects an increase is more likely to find one.
The manufacturer of the airframe I am current on declares that carbon brake wear is dependent on the number of applications and not on braking intensity, adding further that 75% of wear is attributable to taxi out with cooled brakes. So how much of those 25% does happen on the runway and will be affected by the policy? Next, the lowest wear per application is supposed to be at about 220 deg C indicated temp, consequently more strain during the rollout would give you less wear on taxi in. Hmm. Then there is the maybe-not-so-apocryphal story (heard of it on PPRuNe, must be true then) of a BA reverser / autobrake wear assesment which showed more wear with autobrake plus reversers ... on one particular type but with different results on another fleet!? While on the subject of autobrake: idle reverser policy will likely bring manatory autobrake, hence on long runways with far exit, where sensible pilots now may use no autobrake + idle, with ABRK + idle you will get a wear increase plus extended taxi time so $$ out of both windows... We could go on for pages like this.
Best of luck with the assigment, honestly. But I would not bet my personal money on the result irrespective of which one it was (even the one I agreed with)
To rub more salt, chances are the decision whether to proceed or not will neither be a technical one, nor of direct operating costs at all.
regards, FD
* implemented = announced? published ? trained ? executed by line pilots?
.WS I wonder how someone actually does measure brake wear and compare it before / after such policy is implemented (*). At the same time, many a task force / project group would certainly agree there is a brake wear increase, but the distinction between causality and confirmation bias is very hard to make. For sure, one who expects an increase is more likely to find one.
The manufacturer of the airframe I am current on declares that carbon brake wear is dependent on the number of applications and not on braking intensity, adding further that 75% of wear is attributable to taxi out with cooled brakes. So how much of those 25% does happen on the runway and will be affected by the policy? Next, the lowest wear per application is supposed to be at about 220 deg C indicated temp, consequently more strain during the rollout would give you less wear on taxi in. Hmm. Then there is the maybe-not-so-apocryphal story (heard of it on PPRuNe, must be true then) of a BA reverser / autobrake wear assesment which showed more wear with autobrake plus reversers ... on one particular type but with different results on another fleet!? While on the subject of autobrake: idle reverser policy will likely bring manatory autobrake, hence on long runways with far exit, where sensible pilots now may use no autobrake + idle, with ABRK + idle you will get a wear increase plus extended taxi time so $$ out of both windows... We could go on for pages like this.
Best of luck with the assigment, honestly. But I would not bet my personal money on the result irrespective of which one it was (even the one I agreed with)
To rub more salt, chances are the decision whether to proceed or not will neither be a technical one, nor of direct operating costs at all. regards, FD
* implemented = announced? published ? trained ? executed by line pilots?
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Some airport authorities (eg Narita ) request idle reverse only unless more is needed. I forget the exact wording.
This was for noise consideration of the surrounding communities near the airport.
I generally, never used anything but idle reverse unless the runway was wet or contaminated.
In the MD-88 you could cause directional control problems by selecting full reverse because it would diminish the effectiveness of the rudder.
One stormy night at LGA I used maximum reverse on a 727 which resulted in the center engine popping off a few compressor stalls. The tower controller started yelling that we were on fire because of the display.
This was for noise consideration of the surrounding communities near the airport.
I generally, never used anything but idle reverse unless the runway was wet or contaminated.
In the MD-88 you could cause directional control problems by selecting full reverse because it would diminish the effectiveness of the rudder.
One stormy night at LGA I used maximum reverse on a 727 which resulted in the center engine popping off a few compressor stalls. The tower controller started yelling that we were on fire because of the display.
My airline measures the acidity of the hydraulic fluid. The fluid changes Ph due to it being heated by braking . We operated a widebody Airbus for over twenty years predominately using full reverse and manual braking. In the latter years this was changed to idle reverse and manual braking to save fuel. It soon became very noticeable that the brake packs were being replaced more frequently and also the acidity of the hydraulic fluid was becoming noticably more acidic which then led to more hydraulic leaks as the seals were degrading.
Thread Starter
I wonder how someone actually does measure brake wear and compare it before / after such policy is implemented (*).
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Exactly my conundrum.
and I also found this: See Page 20 of this airlines Fleet Newsletter.
http://contentz.mkt932.com/lp/19805/...dec%202014.pdf
Last edited by Goldenrivett; 12th Nov 2015 at 23:06.
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Long runway parking close to the end.
When landing on a 11000 foot runway(3,367 m) and the parking spot is off the left end of the runway, idle reverse on touch down and no auto brakes, had to add just a touch of power when turning off at the end. The aircraft was a 747-200 with a landing weight of about 350k lbs.(220k kilos), first touch on the brakes was at the parking spot. We always advised approach and tower that we would be rolling to the end. A couple of times we were asked to expedite the exit.
Reverse thrust produces better results at the higher speed. Below about 80 knots it is doing nil to help slow the craft.
Companies that demand use of reverse thrust and or us of auto brakes do so because of the lowest common denominator, the weakest captain.
Reverse thrust produces better results at the higher speed. Below about 80 knots it is doing nil to help slow the craft.
Companies that demand use of reverse thrust and or us of auto brakes do so because of the lowest common denominator, the weakest captain.
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What is the cost comparison of brake maintenance when using only idle REV, as is often demanded by many airports, and the cost of brakes using NO REV? This would then bring in the question of what is the cost of installing TR's in the first place. As they are not considered in normal RTOW calculations, nor landing, one wonders are they worth it? There has been smaller jets, Bae146, that didn't have any. People will know of more.
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Brake wear of carbon brakes depends on how many times you use pedals and not on how hard you use them.
So I expect that there will be no extra cost if you use idle reverse.
So I expect that there will be no extra cost if you use idle reverse.
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We got a note from our fleet manager that we're 'tearing up' 748 brakes using the procedures designed for 744s (Flaps 25, idle reverse). Pix included showed brake assemblies with 'major damage'. no indication of similar damage on the 744s.
It should be obvious that when landing a heavier airplane at near its limit weight, using procedures for lighter airplanes may not necessarily work well. While the 748 brakes and tires are bigger/heavier, they are apparently pushing the limits as well.
FWIW, I've adopted the following personal guidelines, to reduce max tire speeds and brake energy:
For takeoff, Flaps 20 at 320 Tonnes or above. That goes along with the concept that the 744 is 'heavy' because bank is restricted with flaps up below Flaps UP+20 speed [FCTM 3.37: "747-400 Above 680,000 lbs (309,000 kgs), limit bank angle to 15° with flaps up until reaching UP + 20 knots."]
For landing, Flaps 30 at 250 Tonnes or above. Max reverse if Autobrakes 3 or above required for landing performance. 250T is the baseline landing weight for performance charts, so I assume anything above that is "heavy".
YMMV, and you may have different views on performance...
It should be obvious that when landing a heavier airplane at near its limit weight, using procedures for lighter airplanes may not necessarily work well. While the 748 brakes and tires are bigger/heavier, they are apparently pushing the limits as well.
FWIW, I've adopted the following personal guidelines, to reduce max tire speeds and brake energy:
For takeoff, Flaps 20 at 320 Tonnes or above. That goes along with the concept that the 744 is 'heavy' because bank is restricted with flaps up below Flaps UP+20 speed [FCTM 3.37: "747-400 Above 680,000 lbs (309,000 kgs), limit bank angle to 15° with flaps up until reaching UP + 20 knots."]
For landing, Flaps 30 at 250 Tonnes or above. Max reverse if Autobrakes 3 or above required for landing performance. 250T is the baseline landing weight for performance charts, so I assume anything above that is "heavy".
YMMV, and you may have different views on performance...