Reverse vs brakes

Bandit_Driver said:
Reverse is most effective at high speeds. Most modern jet engines spool quickly for reverse. However the burst of speed you mention when coming out of reverse too quickly I have only really noticed on the low bypass engine with clam shells. I have not noticed to be an issue at all on the larger bypass fans with translating cowls. I am assuming this due to only the fan air being reversed vs all the air air on the clamshells. I'm sure fadec may also play a part to.

@Derg aka Airbus guru what say you?
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The book I learned this from likely wasn't referring to the modern engines of today. Personally I haven't noticed any small burst of thrust, but the dynamics of it make sense. It seems the E-jet takes a while to deploy and spool the reversers and thrust
 
Bandit_Driver said:
Reverse is most effective at high speeds. Most modern jet engines spool quickly for reverse. However the burst of speed you mention when coming out of reverse too quickly I have only really noticed on the low bypass engine with clam shells. I have not noticed to be an issue at all on the larger bypass fans with translating cowls. I am assuming this due to only the fan air being reversed vs all the air air on the clamshells. I'm sure fadec may also play a part to.

@Derg aka Airbus guru what say you?
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Going straight from max reverse to forward idle is a great way to get that head bobbing burst of speed (as well as tack on an extra 100C of brake temp on an airbus).

Every non-RJ I've flown have had hydraulic actuated reversers, and they move QUICK. Always always always pause at reverse idle and let the engine unspool before going to forward idle.
 
Cav said:
Closing the TR's too fast on the DC9 was a big no no. Regardless of the burst of speed you would also sometimes have difficulty getting the buckets to close and secure properly.
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They technically fixed this issue on the 717 but if you move out of idle reverse before the clam shells are fully open, you get some forward thrust. Also closing them too quickly (sometimes causes a fault message related to not locking fully.
 
PeanuckleCRJ said:
With carbon brakes, it's generally more cost effective to use idle reverse and heat those mofos up. Turn time on the bus without brake fans is more the issue with that.

Steel brakes... use the reversers and brakes a bit less..

Regardless, you use both reverse and brakes every time.
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For us they also talk about number of applications. One long application is better for wear than two short applications.
 
FL350 said:
If you have the tool to use you should use it, especially in the critical time of landing. If you're worried about the marginal cost differences of reverse thrust vs braking then someone probably shouldn't own that airplane. On the jet engine reverse thrust is usually operated by bleed air and their for takes longer to deploy at low engine RPM; all the more reason to select reverse thrust as soon as operationally allowed and use it as long as operationally allowed to. Also reverse thrust should not be quickly reduced from max to min and idle, as you can get a small burst of forward thrust if the engine is not given time to decelerate. Use them until you are satisfied your landing roll will end on the pavement.
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Only reversers I've ever seen operated by bleed air were Aeronca TR's. Everything else has either been electric, or hydraulic.
 
mshunter said:
Only reversers I've ever seen operated by bleed air were Aeronca TR's. Everything else has either been electric, or hydraulic.
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Aeronca TR's are junk, seems like the parts supply has almost dried up. There is an STC to remove the actuators and levers and pin them permanently, I think all learjet operators should comply. Too bad most 55's have Aeroncas and puny brakes. Whoever came up with those Rube Goldberg contraptions should be thrashed about the head and shoulders regularly. Did I mention Aeroncas are junk?
 
knot4u said:
Aeronca TR's are junk, seems like the parts supply has almost dried up. There is an STC to remove the actuators and levers and pin them permanently, I think all learjet operators should comply. Too bad most 55's have Aeroncas and puny brakes. Whoever came up with those Rube Goldberg contraptions should be thrashed about the head and shoulders regularly. Did I mention Aeroncas are junk?
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Yep. I have about 350hrs in '55's. We treated them as emergency help because we were never sure if we'd be able to get them to stow. Had about a 50/50 shot at it. But I also think it had to do a lot with the operator too. Maintenance was an.....after thought.
 
Well I was paraphrasing an outdated book. But I think my main point is that if you have them use them. Obviously close them up when it's prudent to avoid FOD damage
 
On our jet, we use the buckets as much as practical because our brakes are stupid expensive (much like everything else on the airplane) and very sensitive (we have brake by wire on ours). Over a quarter million bucks if you want a complete brake job and around $20K per pad depending on new vs. overhaul. The buckets are hydraulic on the GIV and when we are slowing for taxi, most crews will keep them out and in idle reverse to avoid that thrust bump mentioned by others.
 
PeanuckleCRJ said:
Going straight from max reverse to forward idle is a great way to get that head bobbing burst of speed (as well as tack on an extra 100C of brake temp on an airbus).

Every non-RJ I've flown have had hydraulic actuated reversers, and they move QUICK. Always always always pause at reverse idle and let the engine unspool before going to forward idle.
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CF6s are pneumatic, and have a habit of twisting the transcowl on occasion.

At any rate, hydraulic or pneumatic, let them spool to idle reverse before returning to forward thrust. Ever seen 254 woodpeckers?
 
FlyByWire22 said:
On our jet, we use the buckets as much as practical because our brakes are stupid expensive (much like everything else on the airplane) and very sensitive (we have brake by wire on ours). Over a quarter million bucks if you want a complete brake job and around $20K per pad depending on new vs. overhaul. The buckets are hydraulic on the GIV and when we are slowing for taxi, most crews will keep them out and in idle reverse to avoid that thrust bump mentioned by others.
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The best price we've been able to find recently has been $60K per assy. for BBW GIV brakes, the saving grace is those brakes will last a long time if used normally. I've never heard of any SOP from our ops people for crews to use TRs' over brakes. When I took care of a G150 we would ask the pilots to try to save brakes because normal usage would wear them out in about 300 cycles, if they tried to conserve them we could get 450 cycles out of them. It certainly wasn't a procedure or a policy, just a courtesy when/if the crew was able, saved a decent amount of money in parts/labor for the owner. And did I mention Aeroncas stink?
 
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