duplicate post

 

Had it happen about 3 years ago. Came on at about FL250. Ended up keeping it slow with the lever pulled back to prevent overtemp.

 

I had an uncommanded APR activation on one engine after TO, with both running normally. Think it happened about 1 year ago out of DEN and we just adjusted thrust levers to normal CLIMB power. No big deal.

 

Had this happen a few years back in the RJ departing from ATL where the metal rod that holds up the side of cowling for mx fell behind the throttle cable and held the thrust lever at the forward most stop. Eventually we followed the QRH that had us use the fire switch to shut down the engine. Apparently it is somewhat of a common problem in those planes...at least that's what the mx guy told us.

 

Are you sure that wasn't just a straight up DEC (EEC) failure?

I've had APR trigger for no obvious reason on the CRJ200 and it was not that big a deal. I've also seen it in a light 757 where that sort of thing is a bigger deal because you've got your hands on a whole lot of power. In both cases the engines responded to throttle inputs.

With this recent accident, did they try other methods of shutting the engines down, like the Fire Handle / Button ?

 

Yes, I was referring to the CRJ crash in Africa recently. I'm surprised that there are so many APR failures in this limited sampling.

I don't have anything remotely technical to research the precise parameters for APR activation, beyond the glossed over pilot level knowledge that we are familiar with. For instance, we know that it makes 500 pounds more thrust. If it failed, could it dump enough fuel for 1,000 pounds thrust? If so, how 'bout 10,000 pounds?

Remember, the same core CF-34 *can* make make beau coup power, as it does in the bigger CRJ's and Air Force A-10. The generic limiting factor are temperatures for duty cycle / cost parameters / metallurgy / maintenance costs.

To make power, air is a constant on the ground, and obviously it was burning, so no further source of ignition is required. That leaves fuel. And fuel is delivered with two inputs; mechanical movement of a lever on the engine's fuel controller, and by a schedule from the APR computer routine.

The thrust lever cables didn't make sense to me, since I assumed that the only place that there was a common failure point was at the actual thrust lever quadrant. It seems that was not a good assumption.

I doubt the fuel SOV's failed to shut the engines down. It's more logical that in the seconds before smashing into the building, they didn't get pushed, or if they did, enough momentum had already propelled the plane and its likely overheated brakes couldn't stop it.

An uncommanded increase in thrust is not a thrust lever cable problem. Stuck at a particular setting, even 100%, sure, but not a change in thrust. If the engines were at a power setting that was low enough for them to even get to the chocks, it doesn't make sense that jammed cables were then able to magically raise that setting, if in fact that's what happened.

Hopefully we'll get more accurate data as to the actual thrust lever angles / power output.

By the way, both the CA and FO were seriously injured in this, either losing or breaking bones in their respective lower extremities. At least one person may have been killed in the ambulance while carrying a passenger (but not necessarily anybody in the ambulance).

Does anybody have the specific inputs to the APR? For instance, WOW is neat, but I'm interested in what makes WOW, etc. (e.g. zero volt equals airborne, 5 volts equals WOW).

 

Tony, I've got a copy of the CRJ2/7/9 PRMs at my house. When I get home I'll take a look and see what I can come up with APR. I recall it is related to a TO BIT set with WOW/FLAPS/and PWR >X% N1. If someone else here as access to the Pilot Reference Manual or MX books feel free to speak up...

PA31.

 

Probably have to ask bombardier on that, but I doubt it would be designed to be able to physically add much more than is required for APR...otherwise you create a potential to destroy the engine during an APR event.

I'm pretty sure the cables follow the same path. A structural failure along that path could bend the cable runs, causing uncommanded power changes. I recall one incident where a rapid depressurization caused the floor to buckle, which affected flight control cables and power lever cables.

I think the thrust levers mechanisms themselves are completely separate (for redundancy). They are just located next to each other.

They may not have even thought of it at the time...if not, they are kicking themselves now.

Jammed cables would not change the power setting, but a bent cable run could.

Yeah, I'm curious.

 

Just spoke with a Kenya crew that was staying in our hotel. According to them, both engines went to "wacky" mode, presumably at something close to take off power. The crew shut down one engine, then came back to land.

They lost control of the airplane on landing, with the one engine propelling them to the accident scene. They were never parked.

I don't even know how you'd get that plane to land, and it did take them several attempts.

 

Hi.

Sorry, the Kenya Airways crew was mis-informed.

To hit the tower during/after landing, they would have to have made a 90 degree turn off the runway, and then after travelling 3-400m or so, another 90 degree turn, and they would not have had enough energy left to strike the building with any force.

The tower is nowhere near the runway, and you could not hit the tower on landing unless you landed on the ramp, which they did not do.

I don't know the whole story, but I was there the day of the accident. I heard that they shut down one engine after takeoff, and landed with one engine at full power and taxied back to the ramp. The Jetlink press release says that they were in parking, and "just before they were chocked", or something like that, the brakes failed and the plane taxied at high speed into the tower.

They were in parking on the far side of the ramp from the tower, about 700m or so away, and would have needed that much acceleration room to hit the building at that force.

Accident: Jetlink Air CRJ1 at Kigali on Nov 12th 2009, throttle jam, impacted terminal after return

cliff
NBO