IAS Hold in Climb not accurate

[Ray Proudfoot 8,947]

I've been picking up tips on how better to fly this aircraft and one was to engage IAS Hold and adjust the speed on climb to around 150-180kts. Having engaged that mode and with the throttle fully forward the aircraft is not maintaining the selected speed.

For example I have commanded 185kts but the IAS is only 177kts. I'd expect the aircraft to pitch up until 185kts is achieved.

Is this a known 'bug' and if so is there a fix from Bert the Magician?

[Bert Pieke 7,584]

This is a known defect... all Carenado planes have trouble with IAS modes..

Personally, I stay with the VS mode...

IAS mode kind of works, but as you have noted, the speed is typically off by some 10-15 kts..

BTW,  not to be nitpicking, but getting to 185 kts would require pitching down, not up..

 

[softreset 33]

I brought it up a couple of months ago on the forums -

I reached out to Carenado about it as like Bert indicated, IAS hold is funky. What's odd, though, it works exactly as described on the Cheyenne III and so far is the only Carenado plane (that has IAS mode) which works as described.

[Ray Proudfoot 8,947]

Hi Bert, yes, silly me. Pitch down. 

If v/s mode is recommended is there a guide to speed and climb rates depending on altitude and weight?

OTOH, I could increase the IAS to compensate for the disparity as the g/speed will then increase with altitude. Using v/s means more tinkering to get the best climb rate.

[softreset 33]

https://ucdavis.box.com/v/PC12performance

Page 284 - 300

I set climb power to between 36-36.5 psi of torque and keep IAS between 120-140.

That PDF is from Pilatus, I just hosted it on my personal Box.com account so I always knew where to find it. 

[Ray Proudfoot 8,947]

Thanks Mark. Downloaded and will study diligently.

[mgr 29]

Rough climb schedule:

0-10.000 ft -> 160 KIAS

10-15.000 ft -> 150 KIAS

15-20.000 ft -> 140 KIAS

20 -25.000 ft -> 130 KIAS

25- 30.000 ft -> 115 KIAS