CRJ-200 Climb Speed Envelope/Slow Cruise

C150J

C150J

Well-Known Member
Hi guys,


First and foremost, I completely respect and adhere to company-prescribed climb profiles. That being said, after reading PCL3701's NTSB report, I can't help but think that a lot of profiles were instituted as a knee-jerk reaction to core lock/out climbing the airplane's capabilities. Obviously, you don't want to climb at slow speeds to an altitude where you can't accelerate or overtemp the engines, but:


- How comfortable do you feel climbing below 250KIAS above 10,000ASL?
- How comfortable are you flying slower than 250KIAS enroute?
- What considerations, besides ITTs and ability to accelerate at altitude, must be considered?


We are supplied weight/ISA/speed capability charts for our profiles but no other speeds, so it leaves a lot to curiosity. I feel like it's a hole in our training, as the last jet I flew was straight-winged and slow anyways!


Thanks!
J.
 
C150J said:
Hi guys,


First and foremost, I completely respect and adhere to company-prescribed climb profiles. That being said, after reading PCL3701's NTSB report, I can't help but think that a lot of profiles were instituted as a knee-jerk reaction to core lock/out climbing the airplane's capabilities. Obviously, you don't want to climb at slow speeds to an altitude where you can't accelerate or overtemp the engines, but:


- How comfortable do you feel climbing below 250KIAS above 10,000ASL?
- How comfortable are you flying slower than 250KIAS enroute?
- What considerations, besides ITTs and ability to accelerate at altitude, must be considered?


We are supplied weight/ISA/speed capability charts for our profiles but no other speeds, so it leaves a lot to curiosity. I feel like it's a hole in our training, as the last jet I flew was straight-winged and slow anyways!


Thanks!
J.
Click to expand...

Coffin corner is also an issue. Did they cover this in your training?
 
Blackhawk said:
Coffin corner is also an issue. Did they cover this in your training?
Click to expand...

Yes, absolutely. I'm referring to actual aircraft capability, as our company does not supply us with sub-250 climb charts that DO exist. Coffin corner is certainly an issue, but one that tends to arise in the 30s. I'm wondering if anyone has any insight.
 
Coffin corner isn't really much of an issue in CRJs. The low speed boundary is far more of a concern. It's rare to reach an altitude in a CRJ where the low- and high-speed cues start to come close together. Much different story in other airliners, however.

In the CRJ, you need to be concerned with the low-speed cue. The green line (or was it blue?) doesn't really give accurate information unless you're below 10k and in a landing configuration.

Regarding climb speeds, I always varied my climb speed based upon aircraft weight and winds. If I had a light weight and a strong headwind, I was climbing at much faster speeds (sometimes 310). If I had a heavy airplane and a strong tailwind, I would be climbing at much lower speeds (sometimes 250). I never climbed below 250, though. Not that it's necessarily unsafe, just that you start to lose any economic benefits, and it might interfere with ATC. In fact, departing a large airport, I usually wouldn't slow below 280 until I got a good distance away and didn't see anyone climbing behind me on TCAS.

When you get into a larger aircraft, you'll start using a "cost index" in the FMS, which does all of the calculations for you on what the best speed is for a given economic baseline. Without that, you have to guesstimate it. Anything between 310 and 250 is what I always used, depending on the circumstances.

For cruise, again, it depends a lot on winds. The higher the headwind, the faster the mach, and vice versa.

For descent, I just used flight idle as a goal, which varied between 280 and 300 for a reasonable descent angle, depending upon weight.
 
Thanks ATN!

The green line (1.265 Vso) is only accurate in landing config, as you stated. I'm just trying to get an idea of what's "safe" should we ever need to dip below 250KIAS at higher altitudes, be it for traffic, climbing out of ice, etc.
 
We have a low and high speed buffet chart based on altitude, weight and ISA deviation. It lists the "safe" speed range in IAS and mach. I don't know how the data is actually generated, but that's the SLOWEST speed you can go in that set of conditions. How close can you get to that and still be "safe"? Who knows. The only real guidance we have is our flap operating speed for a given weight + 10 knots. But that may or may not hold true at high altitudes.
 
ATN_Pilot said:
Coffin corner isn't really much of an issue in CRJs. The low speed boundary is far more of a concern. It's rare to reach an altitude in a CRJ where the low- and high-speed cues start to come close together. Much different story in other airliners, however.

In the CRJ, you need to be concerned with the low-speed cue. The green line (or was it blue?) doesn't really give accurate information unless you're below 10k and in a landing configuration.

Regarding climb speeds, I always varied my climb speed based upon aircraft weight and winds. If I had a light weight and a strong headwind, I was climbing at much faster speeds (sometimes 310). If I had a heavy airplane and a strong tailwind, I would be climbing at much lower speeds (sometimes 250). I never climbed below 250, though. Not that it's necessarily unsafe, just that you start to lose any economic benefits, and it might interfere with ATC. In fact, departing a large airport, I usually wouldn't slow below 280 until I got a good distance away and didn't see anyone climbing behind me on TCAS.

When you get into a larger aircraft, you'll start using a "cost index" in the FMS, which does all of the calculations for you on what the best speed is for a given economic baseline. Without that, you have to guesstimate it. Anything between 310 and 250 is what I always used, depending on the circumstances.

For cruise, again, it depends a lot on winds. The higher the headwind, the faster the mach, and vice versa.

For descent, I just used flight idle as a goal, which varied between 280 and 300 for a reasonable descent angle, depending upon weight.
Click to expand...

Not according to Bombardier and the NTSB:

"Situational awareness must be maintained at all times when the aircraft reaches the desired cruising altitude. If the nose attitude (angle of attack) is excessively high, the performance may be such that the aircraft is not capable of maintaining the altitude and the airspeed may begin to decay. Under these circumstances, a descent must be initiated immediately."
...
"The Bombardier chief pilot stated that one of simulator sessions taught by instructors at Bombardier consisted of high altitude flight at FL390. The pilot was able to observe the convergence of the high and low speed cues and then would initiate banked level turns to activate the stick shaker. He said it was a brief but effective demonstration."

In addition the regional airline I flew for experienced it a few times on longer haul flights when the airplane was first fielded in the '90s. The issue seemed to go away after training on the subject was introduced.

Personally I think core lock was a way for lawyers to shift blame for the crash from the aircrew to Bombardier.
 
Core lock was a serious problem, and not something dreamed up by lawyers. ALPA fought hard to make sure the truth was brought forward about it, because Bombardier covered it up for years.
 
ATN_Pilot said:
Core lock was a serious problem, and not something dreamed up by lawyers. ALPA fought hard to make sure the truth was brought forward about it, because Bombardier covered it up for years.
Click to expand...

Core lock, at least in this case, resulted from two pilots getting their engines into compressor stall then not following the air restart procedure. What do you know.... when the tried the air restart at a slow airspeed the engines were fried.
 
Blackhawk said:
Core lock, at least in this case, resulted from two pilots getting their engines into compressor stall then not following the air restart procedure. What do you know.... when the tried the air restart at a slow airspeed the engines were fried.
Click to expand...

This is true, but I want to share the windmill-restart history of the CF34-3B1. General Electric, through testing and analysis of real engine failures, determined that there was a legitimate problem with the CF34's ability to windmill start. On the CL-604, 20% of all windmills were unsuccessful, which was troubling. Engineers improved the hot section, and got the number down to 11% in the 1990s, and eventually to 4% to date. More testing occurred after 3701, to include the airspeeds required to keep the N2 turbine moving.

I'm not disputing the fact that there were CERTAINLY pilot issues with 3701, but the lack of training and aircraft-specific information played a part in that crash.
 
C150J said:
This is true, but I want to share the windmill-restart history of the CF34-3B1. General Electric, through testing and analysis of real engine failures, determined that there was a legitimate problem with the CF34's ability to windmill start. On the CL-604, 20% of all windmills were unsuccessful, which was troubling. Engineers improved the hot section, and got the number down to 11% in the 1990s, and eventually to 4% to date. More testing occurred after 3701, to include the airspeeds required to keep the N2 turbine moving.

I'm not disputing the fact that there were CERTAINLY pilot issues with 3701, but the lack of training and aircraft-specific information played a part in that crash.
Click to expand...

I do know that the air start does require a prominant nose down attitude to get the necessary airspeed. If you have not done it in the simulator you will probably fail the first time and I was surprised when I heard that Pinnacle did not train their pilots on this maneuver prior to the accident- probably why my initial training was quite a bit longer than theirs as many maneuvers not required by the FAA were included in my training.
 
Absolutely the case. 240KIAS will only yield ~12% N2, and 190KIAS will usually bring N2 to the stops. That windmill-restart procedure usually results in 5,000-7,000' of altitude loss, as getting the airplane to 300KIAS (and eventually 320KIAS) is no easy feat.


Blackhawk said:
probably why my initial training was quite a bit longer than theirs as many maneuvers not required by the FAA were included in my training.
Click to expand...

Did you go through CAE? It would be nice if initial was longer in many respects, as the "you'll learn it on the line" mantra only goes as far as programming the FMS.
 
C150J said:
Absolutely the case. 240KIAS will only yield ~12% N2, and 190KIAS will usually bring N2 to the stops. That windmill-restart procedure usually results in 5,000-7,000' of altitude loss, as getting the airplane to 300KIAS (and eventually 320KIAS) is no easy feat.




Did you go through CAE? It would be nice if initial was longer in many respects, as the "you'll learn it on the line" mantra only goes as far as programming the FMS.
Click to expand...

Went through in ATL. Sim training was 23 periods- 10 for me, 10 for the FO, FO's check ride, my check ride, then a LOFT. Ground was also longer than most other regionals.
 
Blackhawk said:
Core lock, at least in this case, resulted from two pilots getting their engines into compressor stall then not following the air restart procedure.
Click to expand...
It resulted from them ignoring the stick shaker/pusher multiple times and trying to FORCE the airplane to stay at FL410.

Unrelated: Our guidance is to climb no SLOWER than .78M
 
NJA_Capt said:
It resulted from them ignoring the stick shaker/pusher multiple times and trying to FORCE the airplane to stay at FL410.

Unrelated: Our guidance is to climb no SLOWER than .78M
Click to expand...

... which led to a dual compressor stall, which caused the engines to fail, which led to the pilots not following the correct restart procedure, which led to two fried engines.
 
NJA_Capt said:
semantics....They messed up.


:deadhorse:
Click to expand...


... which led to a seat swap in the middle of an emergency because they swapped seats earlier in violation of company regulations, which led to the pilots not telling ATC they lost both engines until 10,000', which led to not being able to make it to an airport even though they started the whole thing at FL410.

Yeah, they messed up up big time. It's a matter of picking which one you want to focus on.
 
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