2 ms·

What’s going to be the effect of increased use of the engine? Airlines like to derate their engines for takeoffs that don’t require full performance in order to

What’s going to be the effect of increased use of the engine? Airlines like to derate their engines for takeoffs that don’t require full performance in order to save wear and tear; how much quicker are the engines going to require overhaul due to extraordinary reverse thruster usage? I guess the brakes involve more rapidly consumable items, but this seems like a decidedly suboptimal solution when it knocks a good portion of operating life off an expensive precision jet engine. Sucks to fly in Russia, I guess.

stainablesteel 3y ago
i agree, its not like there's going to be shortage of brakes in the future, that's a rather simple component.
- mannykannot 3y ago
  It's been a while since that was the case, even for road-vehicle brakes. Judging things by their apparent simplicity can be misleading - consider a wing, for example... There's a bunch of non-obvious things you can get wrong.
WalterBright 3y ago
I seriously doubt the thrust reversers significantly shorten the life of the engine for the few seconds they're on. All the reverser is is a couple of hydraulically operated clamshells that close over the exhaust stream forcing it to the side rather than back. Ironically, it doesn't actually "reverse" the thrust. The exhaust stream impinges on the clamshell, pushing the airplane backwards.
- MaxfordAndSons 3y ago
  Ohhhh that makes so much sense than the halfbaked naive implementation in my head involving the turbine somehow reversing the direction of airflow entirely and sucking air from the back to the front.
  - WalterBright 3y ago
    Haha making the turbine run backwards would be quite an engineering challenge. It's heavily optimized to go in one direction. Turboprop airplanes have variable pitch propellers, I don't know if they can change the pitch enough to get reverse thrust.
- kashunstva 3y ago
  > All the reverser is is a couple of hydraulically operated clamshells that close over the exhaust stream forcing it to the side rather than back. Clamshell and bucket type thrust reversal systems are one way of achieving reversal. The latter are mostly seen on low-bypass turbofans. Large high-bypass engines often use a cold-stream reversal “cascading” system that is more complicated and includes both shunting of the exhaust vector and blocking air intake into the combustion stage. You’ll see this in action on engines where the rear cowling slides backwards to uncover the cascading vanes.

stainablesteel 3y ago

i agree, its not like there's going to be shortage of brakes in the future, that's a rather simple component.

mannykannot 3y ago
It's been a while since that was the case, even for road-vehicle brakes. Judging things by their apparent simplicity can be misleading - consider a wing, for example... There's a bunch of non-obvious things you can get wrong.

WalterBright 3y ago

I seriously doubt the thrust reversers significantly shorten the life of the engine for the few seconds they're on. All the reverser is is a couple of hydraulically operated clamshells that close over the exhaust stream forcing it to the side rather than back. Ironically, it doesn't actually "reverse" the thrust. The exhaust stream impinges on the clamshell, pushing the airplane backwards.

MaxfordAndSons 3y ago
Ohhhh that makes so much sense than the halfbaked naive implementation in my head involving the turbine somehow reversing the direction of airflow entirely and sucking air from the back to the front.
- WalterBright 3y ago
  Haha making the turbine run backwards would be quite an engineering challenge. It's heavily optimized to go in one direction. Turboprop airplanes have variable pitch propellers, I don't know if they can change the pitch enough to get reverse thrust.
kashunstva 3y ago
> All the reverser is is a couple of hydraulically operated clamshells that close over the exhaust stream forcing it to the side rather than back. Clamshell and bucket type thrust reversal systems are one way of achieving reversal. The latter are mostly seen on low-bypass turbofans. Large high-bypass engines often use a cold-stream reversal “cascading” system that is more complicated and includes both shunting of the exhaust vector and blocking air intake into the combustion stage. You’ll see this in action on engines where the rear cowling slides backwards to uncover the cascading vanes.