Climb Rate and Service Ceiling

[kneighbour]

I am having trouble flying this plane at the stated service ceiling of 25,000'. In fact, I have never got there. The most I have been able to squeeze out of it in a reasonable time is 22,000'.

 

I usually use the Climb function on the autopilot - setting the speed at L (140kts). When the plane gets to around 15,000', this means a climb rate of around 1000 fpm and dropping. At 18000', it has dropped to around 500 fpm or less. So climbing to 25,000' will takes ages with the climb rate approaching 0 all the time.

 

If this is normal, then not a problem - I will just fly at 17,000' or so, which is achievable in a reasonable time and with only a little effort.

 

I realise that there are several variables involved here , but we can assume 50% fuel (or less) and 15 passengers. A fine sunny day in Queensland and CL either to Max or 1330 (does not seem to make much difference). Torque set to 60-65 (pretty much maxxing out the Temp).

 

 

[JGregory]

You can't fly all the way to 25K using climb (L).  When your vertical speed declines you will need to switch to "M" or "H" for the remainder of the climb.

[kneighbour]

Sure - I should have thought to mention the different Climb settings. But are very low climb rates (<500 fps) at these heights normal?

[JGregory]

Yes, it is typical for most aircraft to climb at lower rates at higher altitudes.

[kneighbour]

Yes, it is typical for most aircraft to climb at lower rates at higher altitudes.

Well, of course. But is less than 500fps (like 200-300 fps) normal?

[Goran_M]

Depends on weight, temperature, wind, baro pressure, climb mode, engine power setting, etc...

The higher you go, the less torque the engines put out at the original PL setting.  So feel free to increase Power by adjusting the Power Levers as you climb.

Just keep an eye on your torque gauge.

[breadwild]

For what it's worth, in checking  even long flights by Silver Airways on FlightAware, the highest is usually FL230

[ointment]

...500fps (like 200-300 fps) normal?

Not to be an ass, but I believe you mean fpm rather than fps.  

[kneighbour]

Not to be an ass, but I believe you mean fpm rather than fps.  

indeed I do! 

[jailer]

You can't fly all the way to 25K using climb (L).  When your vertical speed declines you will need to switch to "M" or "H" for the remainder of the climb.

 

I'm a bit confused by the climb profile of this airplane.  It would seem to me that the "low speed" climb should have a higher rate of climb than a "high speed" climb.  This is consistent with the performance charts included in the package.  For example, the chart shows that for 20000 lb FL 250, ISA conditions, 15 minutes at LOW and 18 minutes at HIGH.  Am I missing something?

 

In any case, I'm getting nowhere near the time or distance values indicated in ISA conditions at max climb power.  I've tried RPM at 1250-1330 as indicated on the chart, as well as leaving it at the condition levers at MAX, all without any noticeable change.  It's very confusing.  

 

I can accept that most real life trips would not be at/near the service ceiling, but I would expect a study level sim to match the calculated performance, so just wondering if I'm doing something wrong here.

 

(I apologize in advance if it's the improper etiquette to revive this thread, but I only recently got this plane and it didn't make sense to start a new one.)

[JGregory]

I'm a bit confused by the climb profile of this airplane.  It would seem to me that the "low speed" climb should have a higher rate of climb than a "high speed" climb.  This is consistent with the performance charts included in the package.  For example, the chart shows that for 20000 lb FL 250, ISA conditions, 15 minutes at LOW and 18 minutes at HIGH.  Am I missing something?

 

In any case, I'm getting nowhere near the time or distance values indicated in ISA conditions at max climb power.  I've tried RPM at 1250-1330 as indicated on the chart, as well as leaving it at the condition levers at MAX, all without any noticeable change.  It's very confusing.  

 

I can accept that most real life trips would not be at/near the service ceiling, but I would expect a study level sim to match the calculated performance, so just wondering if I'm doing something wrong here.

 

(I apologize in advance if it's the improper etiquette to revive this thread, but I only recently got this plane and it didn't make sense to start a new one.)

We are currently in the process of testing some of the flight model in specific circumstances.  We will let you know what we find.