CRJ-100/-200 Automatic Power Reserve
 

Has there ever been an instance of uncommanded activation of APR ?

What are the parameters for activation of ARP?

Lose an engine within 5 minutes of takeoff, APR kicks in...something like 2% 500# thrust/side...

...is that the talk about why there's a CRJ in the VIP lounge?

Cheers
George

Hi.

THe VIP lounge reference is about a CRJ-100 crash in Kigali, Rwanda, where an engine was at full power and could not be shut down. The plane's brakes failed and it crashed into the tower building. The other engine was successfully shut down after takeoff.

cliff
NBO

I'm sure there has been, but I can't find any proof.

If you meet the parameters to arm APR, then the only requirement for activation is a drop below 67.6% N1.

I never had an uncommanded activation of APR, but twice while doing a reduced thrust takeoff I had one engine decide to bump up to TOGA power halfway down the takeoff run.

Funny you should mention this. The airplane I flew yesterday had the APR deferred. It came on umcommanded in flight for a previous crew but apparently it wasn't an issue as the engine responded the the throttle inputs just fine.

Details
 

Anyone have the breakdown on what exactly took place. I saw where someone said they shut one down in flight and returned to the field SE. But then why would you taxi to the gate with one engine running wide open? I think I would have stayed on the runway with the AC pointing in a safe direction ( Like a grassy area )until we could get the thing shut down.....was the Engine fire Push swith not pushed?....details anyone?

I had a similar instance to this out of MSP a year or so ago. APR just came on out of nowhere, stayed on for a few minutes and went off by itself. Unknown why it was tripped, nothing was abnormal prior to it going off.

APR would not have caused this accident IMO. It simply boosts the fuel schedule...ie it adds some fuel to what is already manually selected. If you are at flight idle, APR would simply increase RPM a little bit...it would not cause th engine to go to full power.

If BOTH engines were at full power, there is only one common point between the two engines that I can think of: The throttle cables (they are cables on the 100/200). A structural failure along the path of the cables might have pinched them and jammed them so they could not be moved. Or they might have been cut or broken, which would leave the engines in whatever power setting they were selected at when the cables failed.

Also, you don't need the throttles to shut the engines down, the respective Fire Switchlight will do it for each engine. If the throttles cables AND the fire system failed...well they would be very lucky to get on the ground in one piece, cuz there must have been some serious problem with that airplane.

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

The following is for the purposes of education and no knowledge of current revisions is implied.

"3. Operation
A. With the APR system armed, if the N1 fan speed decreases to 67.6 percent or lower on one of the two engines, the control amplifiers will receive a signal to schedule a fan speed increase for the remaining engine. The speed of the engine, at the usual takeoff N1 speed, will increase by approximately 2.3 percent and the engine that has the N1 drop, will revert to N2 mode and will not follow N1 commands. (For description of N1 and N2, refer to 73-20-00).
NOTE: The APR does not change or cancel the thrust reverser lever inputs to the main fuel control. It is also possible to move the throttle levers and get power settings higher than the usual (non-APR) takeoff thrust.
B. With higher than usual takeoff thrust settings, followed by a loss of power on one engine, the serviceable engine will have a higher turbine temperature (ITT) The data concentrator units (DCU) will change the ITT red line from 900°C to 928°." -bombardier crj-200 aircraft maintenance manual

After takeoff tonight the APR engaged on both engines without reason. I wasn't timing it but we discussed when it finally disengaged and seemed as if it disengaged right at the 5 minute mark where APR is normally disarmed after takeoff. Both engines responded to power lever movements. Maintenance said to continue and it would be deferred after landing. It wasn't really an issue.

200 or 700 atlmsl?

The short bus.... 200