Is there any way to set the display under the IAS ribbon back to True Air Speed instead of Mach percentage? TAS is much more useful in setting up cruise power and when trying to stay under 250 below 10k’.
Why would this be more useful?
Even at low altitudes crz speed is in Mach and the 250kts limit is an IAS limit.
2 Likes
As PZL104 says, 250 kts below 10.000 ft limit is IAS/CAS not TAS. Also I’ve never flown an aircraft were cruise power depends on TAS.
Here’s a screenshot of TBM’s own web page for the 940 - note that performance speeds are listed in TAS:
Please direct me to any piston or turboprop GA aircraft manufacturer’s web page that lists cruise speeds in terms of Mach percentage.
1 Like
You are talking about turboprops?
In this case the 250kts limit below FL100 doesn’t make sense.
Even high speed climb in the TBM is only 170kias (which is very fast for a turboprop)
Btw. the climb tables include Mach number in the ‘high speed’ case (M0.4).
Even a C-130 at MTOW climbs only at 180kias.
1 Like
Granted, you’ll probably never see that speed during climb, but when descending, you still have to be careful. Besides, my main concern is cruise speed.
1 Like
I don’t understand. Why is it a factor during descent? (230kias in case of the TBM).
For cruise power settings you normally use IAS or Mach.
Since IAS is already on the speedtape, Mach makes sense.
The cruise performance tables on turboprops (including the TBM) are usually showing IAS and TAS.
On the real TBM the speed is also displayed in Mach.
OK - let’s forget about the 250 limit for a minute. Daher’s own data lists the max cruise speed at FL280 as 330 KTAS, and long range cruise as 252 KTAS.
I still have yet to see any information regarding cruise speed in % of Mach. I can, however, show you a rather reliable reference that does use True Airspeed, and that would be the Pilot’s Information Manual hosted on TBM’s own website:
https://www.tbm.aero/wp-content/uploads/2016/03/PIM-930__AN__E0.pdf
1 Like
Isn’t TAS on the PFD in the lower left corner?
1 Like
If it is, I’ve never noticed it. I’m firing up my sim now to test. If it’s there, I’ll mark your reply as the solution.
Again, climb speed is in IAS/Mach and the cruise speed tables in IAS/TAS.
I really don’t understand your problem and why you want to switch to an unrealistic speed display.
Correct. It’s that way on most aircraft, including the TBM (787 etc.)
Thanks for pointing my eyes where they usually don’t look! I’ll use this from now on when setting up my cruise phase.
1 Like
Interesting. I noticed this also. I was sure TAS was displayed in a box right below the airspeed tape where I would normally see it. Now it displays MACH. Was wondering if there was a way to change it back. Confirming cruise performance in the TBM per the POH is done via TAS, not MACH which I just wouldn’t use in the TBM at all.
Which manual are you referring to?
I’ve got 5 TBM manuals, 2 different 930 manuals and all 5 have IAS/TAS in the cruise tables.
Why. The real one displays Mach as well.
I’m sure they’re all similar. We’re saying the same thing - The TBM POHs show cruise tables in IAS/TAS. The point isn’t that the real one displays MACH. I understand that. The issue is not being able to choose between the two or show both. Right now, I only see MACH and don’t see TAS anywhere, unless I’m missing something as I did see it before. I’m using the WT G3000 mod of course.
@Fmgc320 Did you notice that this thread is marked as Solved?
I see that now, thanks! And see where TAS is as well. Not sure how I missed it but I did.
Still doesn’t explain why you want to use TAS during flight. Those POH tables are solely for flight planning purposes, you don’t use that to set cruise power as you stated earlier.
You set the cruise power as described in the POH which will result more or less in the TAS from the table, you can use this together with wind data to determine groundspeed and therefore time and fuel required for flight. You are not supposed to adjust the cruise power depending on the TAS achieved.
In other words it doesn’t have much practical purpose in flight, its meant to be used for flight planning purposes. I don’t recall ever using TAS in flight, inflight performance tables are often in IAS/CAS, TAS is merely an intermediate step in calculating the groundspeed (which is directly displayed anyway).
I’m not 100% familiar with the TBM. Besides a Vmo, does it also have a Mmo described? I have flown turboprops with both a Vmo and Mmo limit, in which case MACH indication makes perfect sense…
1 Like
No Mmo on the TBM, but if you are using high speed climb you have to use Mach, since the crossover altitude is FL230.
1 Like