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0D1N

Climbing above FL30

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Hey folks,

 

Great job team that have come to together to make this project possible. One minor question. This aircraft climbs like a bat out of hell, which I like, but when it gets up about FL30 and above the climb gradient is significantly decreased. Is that a real life feature of the CRJ? I've been using the SPD mode to climb, then I have to switch to VS above FL30. In the past few flights I am finding myself to move my throttle position from "CLB" to "MAX" to prevent a major speed decrease.  Any help will be appreciated. Thank you

 

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Hi,

 

why do you "have" to switch? I think the SPD mode can be active until reaching cruising altitude. I always take off, increase speed to 250kn and above FL100 to 290kn until cruising altitude. Please correct me if I am wrong.

 

Greetings

Lukas

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I have tried that, but for some reason it will stop the climb to maintain my speed. Like right now I'm cruising at FL350 and my speed is decreasing with full throttle, I don't know why its slowing down.  I'm decreasing my altitude to FL270 to see if I have better performance.

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Are you using real weather and/or "canned" weather from a weather machine like Active Sky?

"Broken" weather (too high temperatures, deviating massively from real world conditions) could cause this issue, for example.

 

Or are you experiencing "normal" weather, and your climb performance issue has been repeating itself with every flight?

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I've been using ActiveSkyV4, could that be the problem? All this issues has been when I've been using activeskyv4

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Which "speed" are you talking about in the climb?
IAS? Mach Number?

 

It is entirely normal that the IAS can't be maintained all the way into the high levels in any jet, not just in the CRJ.

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It's one of several possible causes. Because by and large the CRJ-700 and -900 are pretty powerful machines. (The -200 - not part of the AS package - not so much.)

 

For a test, you could keep flying the CRJ, but change the weather in ASP4: Try some random historical weather, fly for a couple of minutes, maybe change the weather again. Check for differences in aircraft performance.

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6 minutes ago, Emanuel Hagen said:

Which "speed" are you talking about in the climb?
IAS? Mach Number?

 

It is entirely normal that the IAS can't be maintained all the way into the high levels in any jet, not just in the CRJ.

235 below 10,000. 280 until about 20,000 then .70 Mach.

 

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6 minutes ago, Enter display name here ;) said:

It's one of several possible causes. Because by and large the CRJ-700 and -900 are pretty powerful machines. (The -200 - not part of the AS package - not so much.)

 

For a test, you could keep flying the CRJ, but change the weather in ASP4: Try some random historical weather, fly for a couple of minutes, maybe change the weather again. Check for differences in aircraft performance.

Ok I will give that a try

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23 minutes ago, 0D1N said:

235 below 10,000. 280 until about 20,000 then .70 Mach.

 

 

These are rather slow speeds, try 250/290/.77 and see if that gives you better results. At .70 you might already be getting onto the backside of the power curve.

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Both aircraft can climb to FL 370 when fully loaded at take off. But that is for ISA temperatures. Make sure you do not have a warm weather and anti-ice is off.

The flight planning handbook differentiates between two climb modes:

250/290 KIAS/0.74 M “Normal Climb Speed”
250/320 KIAS/0.77 M “High Speed Climb”

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And you should NOT use vertical speed in climb - especially not above FL 300. In speed mode, you are protected against your airspeed falling too low - you have absolutely no protection if you use v/s. Trying to "force" a greater climb rate than the aircraft is capable of under the current weight and weather conditions, will lead to what you described... falling airspeed and the need for more and more thrust, because you are on the back side of the power curve.

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just did a flight, I used the new numbers for climb out and it worked. I was behind the power curb as mentioned before. Thanks for the help guys!

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Tried in the CR7 with 60% fuel, 56 pax and 1.000 lbs cargo. No weather (as an approximation for ISA). Used 0D1N's numbers and managed a climb (clb detent only) to FL410 quite easily. The only issue was a rather pronounced, but slow and damped pitch oscillation, but the average ROC was OK. (The lowest no./fpm during such a cycle isn't overly impressive, though, so don't look at your VSI at the wrong moment. :P)

 

M 0.70 may be considered too conservative for a powerful CR7/9, but it's not yet behind the power curve (it's still M 0.7, after all). Weather, weight, anti-ice, whatever must still have been a factor, too, I reckon.

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On 8/27/2017 at 10:36 PM, JRBarrett said:

And you should NOT use vertical speed in climb - especially not above FL 300. In speed mode, you are protected against your airspeed falling too low - you have absolutely no protection if you use v/s. Trying to "force" a greater climb rate than the aircraft is capable of under the current weight and weather conditions, will lead to what you described... falling airspeed and the need for more and more thrust, because you are on the back side of the power curve.

 

Use VS in the climb a lot to avoid the oscillations that you get using speed mode, as long as you monitor your speed and don't try to climb at a ridiculous rate it is fine.

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Using CLB mode or VS mode can be company procedure. the CLB is fine with good weather but when things are a bit bumpy, VS more stable but you need to watch speed and switch from IAS to mach as per climb table mentioned above.

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