To other operators of the the Cheyenne series and especially the 2XL, what TAS do you see?

My airplane is a 2XL with 135 engines, speed stacks, and the American aviation cowls. The engines make book power on the torque gauges. Today I saw 255 TAS at 24000 and 2F which is about 15 degrees above ISA. That seems slow to me. The book says I should be seeing 260-265. Engine torques are 1115 and ITT 720, which is what the book says it should be.

I had the gear doors adjusted soothed are tight and that didn't help. I am not sure where else to look.

For what it is worth, the Cheyenne II with 135A upgrade that I used to fly often got 268 ktas at FL250 on a normal day, typically 8-10 above ISA and hotter.

They obviously are shorter and don't have air cycle machines robbing power.

From what I have heard from operators that sounds like where the XL usually runs. You would see a bit of improvement on the 135A conversion I believe.

In my experience over the years the Piper book numbers are pretty optimistic.

We used to get 265-270, but we optimized the CG by paying attention to where people sat, and the baggage load.

Running with a forward CG will cost you 5-10 knots.

It is usually just me and full fuel. Occasionally a passenger that sits up front. I have some items in the back luggage area but not more than 40 pounds worth. I might try putting some additional weight in back. I will do some CG calculations.

Thank you for the advice.

with two aboard and full fuel you want absolutely nothing in the forward baggage, and you may need to add more than 100 pounds in the aft baggage, as far back as possible. to help with the CG.

Garmin Pilot is a good app for W&B because you can create objects that you commonly have, assign them weights, and move them about as needed very easily to fine tune the CG.

With just two aboard it would be best to have the passenger sit in the farthest aft seat.

I know this is not what you asked, but I love threads with real world actual performance examples so we can all compare notes. Thought I'd contribute...

My Cheyenne II with stock -28's, American Aviation scoops & stacks commonly does 255 KTAS on about 85 gph from about 16,000 to FL190. Speed and fuel flows drop to 240 KTAS on 68 gph at FL250, in a linear fashion.

I flew a stock II with stock scoops & stacks for a while and it was about 15-20 knots slower at the same ITT / fuel flows.

There was a IIXL here that I flew with stacks and cowls and 250 KTAS was a good day. 245 everyday.

I flew the airplane that Doug mentioned for 1500hrs, never saw anything above 255kts, it was 250KTAS/500PPH @ 25,000ft.