RJ (Canadair) Flaps problems

[arff]

As an ARFF Fire Officer, I have been confronted lately with numerous emergency calls for RJ's with flaps problem (partial flap, and warning indicators). Is it because these flaps are electrically controlled that they present so many problems ? Is it a wide spread problem ? As a pilot of an RJ (Canadair) with partial flaps or flapless situation how much runway do you use (bare & dry for the runway and average weight for the aircraft)? Thanks.

[Elliot Moose]

The flaps have long been a bit of a weak point in the system for the CRJ. Originally designed for the Challengers, the 100/200 flaps just didn't stand up to the reality of short haul airline ops. Numerous fixes have been made, as well as speed restrictions, and thus the new ones are much less prone to failures.
They are electrically driven, but the problems have come from a variety of sources such as a tendency to twist, and a complex drive system that uses two power drive units, to run a flex shaft which powers the actuators. Just about any little thing out of tolerance and "bing" you get a flaps fail message, and the flaps disable themselves.
The biggest cause of a lot of the problems has been the culture in some airlines of using the flaps as a form of drag control. Comair in particular is known for flying max speeds as long as possible and then dumping flaps at absolute maximum speeds as a way to slow down at the last second. Many pilots either don't notice that they are doing it, don't care, or are completely oblivious to the fact that such hard use (while still within the airframe limits) is needlessly causing things to burn out. For them, the result is an average of about one per day on their fleet of 120 odd airframes. Companies that baby things a bit have much less problems.
As far as landing goes, full flap Vref is in the 130-140kt range depending on weight (give or take a bit) and that gives 2700 to 2900 foot actual landing distance near sea level. Zero flaps has a 30kt correction factor to the full flap speed (160-170kts) and a landing distance 1.65 to 1.70 times the full flap distance (meatball numbers 3600 to 4000 feet). This makes for a very fast approach, and one that can easily eat up a pile of runway, consequently pilots tend to be a bit nervous about doing it!

As an aside, the 700 and 900 series have a different system, as well as leading edge devices which have the combined effect of virtually eliminating the flap problems, while at the same time ensuring at least some form of flaps available in the event that a failure actually does happen.

[used2flyboeing]

I SEE MOOSE"S POINT & I'll RAISE YA ONE ..( Im assuming you are talking about the RJ200 ) - THE CRJ700/900 have no problems like this ..

The FAA issued an airworthyness directive on the Bombardier/Canadair CRJ200 pertaining to an unsafe flight control ( trailing edge flap ) asymmetry ( skewing ) condition. This was caused by unforeseen excessive loading of the flap actuators during operations in particular areas of the flight envelope at certain flap settings. In this condition, the EATON ballscrew actuators break teeth in their hypoid gearsets resulting in a jam condition. The unsophisticated open-loop design, does not detect the problem and therefore allows the power drive units to continue to drive the jamed actuator resulting in a torsional skewing on the associated flight control – resulting in unsafe asymmetric control and potentially loss of roll control of the aircraft. In response, a team was formed between Bombardier; EATON and ELDEC/CRANE to 1) determine design responsibility and 2) solve the problem. It is my understanding the FAA mandated ( AD ) a skew detection system to be implemented – hence ELDEC/CRANE’s involvement. In parallel, EATON responded by redesigning the gearset to non-SAE standards – the challenge to realize a gearset that would fit the existing space envelope and load requirements. This was done by deviating from SAE practices by optimizing the gear cut and choice of materials. The new EATON product has exceeded expectations in robustness. The AD comprised an odeometric position sensing system on all actuators where the synchronicity of the flap actuators is monitored and compared. Actuator position disagreements will cause an immediate shutdown of the flap actuation system. The system resembles a variation approach to the ELDEC supplied 737 NG / 757 ballscrew target. Wherein the Boeing systems rely on a ballscrew-end target. The CRJ200 solution relies on a target that resembles a ballscrew “slip-ring” – similar to a slip ring on an electric motor armature – located “at the other end” of the ballscrew, adjacent to the actuator housing. The system works basically very similarly – perhaps identically to the Boeing system. Either way, Bombardier has responded & beat this thing to death - should be no more issues with it - Even Luftansa Tecknic has jumped on the bandwagon & has engineered their own actuator for the CR200 ..