News just reported CRJ crash...

[Erlanger]

The 3 things I wrote above is fact and doesn't say anything about how the crew handled the situation, though I guess you could read into each one of those. The other stuff I didn't write has to do with what they did or didn't do and it can be debated all day long till we're blue in the face. We weren't there and who knows how we would handle it. The 3 things I mentioned seemed to be fact to me while the other stuff is subject to interpretation.

 

[T-Gates]

Fair enough.... I'm just trying to remain skeptical of everything until all the cards are on the table. If your source at PCL is deep within the investigation and is privy to all this information, he should know to keep his trap shut.

 

[lancair360]

Does anyone know how this cryptic FMS message UNABLE CRUISE ALT is calculated in the FMS?. Is it based upon engine peformance, aerodynamics, etc. Does UNABLE CRUISE ALT translate into a greatly increased risk of aerodynamic stall and dual engine failure in level flight?

 

[PCL_128]

It's just a digital version of the performance charts. It takes into account your weight, VNAV programmed speed, and ISA deviation to decide whether you can make it to an altitude or not.

 

[Oakum_Boy]

Also could be your TOC is beyond TOD.

 

[lancair360]

So basically, an UNABLE CRUISE ALT message is a heads up that you would need to reduce airspeed and/or rate of climb to claw your way up to FL410... i.e. you couldn't maintain both .74M and 500fpm during the entire climb per the profile. Doesn't mean you "couldn't" make it up that high though.

 

[DoinTime]

So basically, an UNABLE CRUISE ALT message is a heads up that you would need to reduce airspeed and/or rate of climb to claw your way up to FL410... i.e. you couldn't maintain both .74M and 500fpm during the entire climb per the profile. Doesn't mean you "couldn't" make it up that high though.

I believe the FMS database uses 300'/minute climb rate and the speed is adjustable in VNAV menu. The PCL performance books authorize a .70M climb speed that guarantees maneuvering at approved altitudes. A 38,000 lb CRJ will make it to just fine to FL410 at ISA temps, 300'/minute climb, and .70M.

 

[regionalcap]

I was looking at our climb chart today and 36000 was the weight limit to make it to FL410 on a ISA day.