IAS Airspeed In a Bravo

[IgorD]

Hello Bravo pilots.  I have owned my Bravo since September of 2021 and have done a factory engine along with a complete Garmin panel.  However I am wondering what is the average speed that you get.  I feel that I should be getting better than 160 TAS at 70% at 6500.  I had taken it up to 17k and was getting 180 TAS with same power settings.  I usually fly with 23/30 settings ROP.  Could it be rigging or this all you get with a Bravo?  When filing a flight plan at 160kt I always end up getting better speeds than forecasted.  

[Rick Junkin]

@IgorD At 70%, as calculated from a fuel flow of 13.2gph LOP, I see 142KIAS at 6K' and 136KIAS at 15K. Standard day true airspeeds are 155KTAS and 171KTAS respectively. For completeness of data for comparison to yours, I run 30"/2200RPM at 13.2gph. I'm almost always near full gross at takeoff with CG at 46" +/- 0.2" My engine has about 1100 hours on it.

EDIT: I have TKS as well.

What fuel flow are you running at 30"/2300RPM?

[IgorD]

4 hours ago, Rick Junkin said:

@IgorD At 70%, as calculated from a fuel flow of 13.2gph LOP, I see 142KIAS at 6K' and 136KIAS at 15K. Standard day true airspeeds are 155KTAS and 171KTAS respectively. For completeness of data for comparison to yours, I run 30"/2200RPM at 13.2gph. I'm almost always near full gross at takeoff with CG at 46" +/- 0.2" My engine has about 1100 hours on it.

What fuel flow are you running at 30"/2300RPM?

Running 17.5 GPH 1590 TIT.  I tried to run it LOP however TIT at that FF would be at 1650 and loss of speed would be almost 15KTS.  

[skykrawler]

Does your bird have TKS?  That'll cost a few kts, maybe 5.

 

[Fritz1]

my benchmarks at 17,000 ft are 185 KT TAS 2250 RPM 30.5" 18.5 GPH 1580 TIT 380 hottest CHT typically on #4 cylinder, GAMI injectors, about 0.3 GPH spread, 900h on a factory reman, I have TKS which I think scrubs off 3-5 KT, typically take off at gross, any luggage goes as far aft as possible, I tried 90% power 24/34 for short periods to see what it does, flow goes to 21.5 GPH to keep temps in check, speed increases by about 11 KT, the fastest I have gone for short periods of time with that power setting is 205 KT in 21,000 ft, sealing the baffles really helped my temps, Tempest fine wire plugs appear to reduce TIT, more complete combustion in the cylinder, extrapolating all that to 25,000 ft the TKS Bravo will probably reach 215 KT TAS with throttle and prop firewalled, fuel flow will probably go to 23--24 GPH, the highest I have taken the Bravo is 23,000 ft, boost started dropping off from 34" passing 21,500 ft, passing 22,000 ft climb was getting anemic, something like 300 ft min, sweet spot for the Bravo is between 19,000 ft and 21,000 ft, everybody believes their own press, that in mind I think this is about as good as it gets in a piston single, anything that goes any faster costs at least three times as much to operate, the weak spot on the Bravo is the exhaust, it really pays to keep TIT below 1600, I check the exhaust for cracks religiously every 25h oil change, none found so far, keep fingers crossed!

[IgorD]

If we are going somewhere far it does make sense to go to 15-17k however my local flights 200 or under I stay at 6-8k.  What do most Bravo drivers get for TAS under 10k?  

[hazek]

~160TAS for me at conservative 65% or so ROP

[slowflyin]

8K, 29/2400 or 30.5/2250, 172-174 TAS.   

[hazek]

Saw 141 IAS today for a 174 TAS at FL105 at 65% (27/22)

EDIT: correction, 169 TAS

[IgorD]

Interesting I may need to see if it needs to be re-rigged.  It had a gear up landing by previous owner.  I was out on Sunday and saw 144 IAS which resulted in 160kt+- TAS at 6.5 and 7K. 

 

Another thought I had after looking at other Bravos on Flight Aware ground speeds are not much different than mine.  I always run my engine at 70% based on G3X and it could be that TAS is being displayed inaccurately.  A bug that got stuck in the pitot tube preventing from getting proper IAS?  Next time I am out I will try to do a four way course to get GS and average them out.

[Fly Boomer]

11 minutes ago, IgorD said:

Next time I am out I will try to do a four way course to get GS and average them out.

Try this instead:

https://www.eaa62.org/technotes/speed.htm

 

[Groomsy]

On 9/15/2025 at 3:12 PM, IgorD said:

Hello Bravo pilots.  I have owned my Bravo since September of 2021 and have done a factory engine along with a complete Garmin panel.  However I am wondering what is the average speed that you get.  I feel that I should be getting better than 160 TAS at 70% at 6500.  I had taken it up to 17k and was getting 180 TAS with same power settings.  I usually fly with 23/30 settings ROP.  Could it be rigging or this all you get with a Bravo?  When filing a flight plan at 160kt I always end up getting better speeds than forecasted.  

This is what I have for settings. I usually cruise at 30” give or take. I keep my cylinder head temp around 340 and burn around 17 gph. 190kts is pretty common up in the teens TAS. Engine has 300 hours and plane has 1150 TT

[LANCECASPER]

3 hours ago, Groomsy said:

This is what I have for settings. I usually cruise at 30” give or take. I keep my cylinder head temp around 340 and burn around 17 gph. 190kts is pretty common up in the teens TAS. Engine has 300 hours and plane has 1150 TT

While running your TIT at 1644 is under the POH max, running that TIT temperature you will go through cylinders and exhaust systems on the Bravo engine. 

Normally we all think of the POH as the final authority but if you take into account all of the experience that Bravo owners on this forum have, in 36 years now since the M20M was introduced, the recommended setting for longevity on this engine is a max combined number of 53 (MP + RPM; Example 29MP + 2400RPM).

Also keeping the TIT below 1600 will prolong the exhaust valves, exhaust system and TIT probes. The POH was never revised from the original and it says 1750 max, but that's when in the early life of the M20M people were going through a set of cylinders every 200-300 hours. The early M20M owners fought the battle and eventually Lycoming devleoped the wet-head (Bravo) engine, which helped. However still even with the Bravo (wet-head) engine you'll still never hit TBO if you run POH numbers.

The other big thing with this engine is that the TIT probes really only last 200-300 hours - less if you run it hotter than 1600. When the probes fail the TIT reads low, compounding the problems. As an example someone runs it at 1650 indicated when in fact the TIT is really 1750 since the probe is bad. This will mean turbo overhaul, exhaust overhaul and cylinder replacements. Looking over the logs and seeing when the probe was last replaced is very important.

I've had three M20Ms and there are a lot of other people on here with a lot of M20M time as well and that's what we have learned so far. 

[kortopates]

He’s probably flying that high power setting believing his engine monitor saying it’s only 65% power! Yet it’s over 80% depending on altitude.
one generally can’t use the %power displayed on their engine monitor till they calibrate it.

Sent from my iPhone using Tapatalk

[Rick Junkin]

23 hours ago, Groomsy said:

This is what I have for settings. I usually cruise at 30” give or take. I keep my cylinder head temp around 340 and burn around 17 gph. 190kts is pretty common up in the teens TAS. Engine has 300 hours and plane has 1150 TT

Several things catch my attention here.

First, your TIT is 1644 and your highest EGT is 1517. That's unlikely. The TIT is nominally 70-100Fº higher than the average of the EGTs, and yours is 126Fº higher than your highest EGT. This COULD be accurate depending on the placement of your EGT probes, but doesn't track with what I've seen in my airplane or in a couple of other Bravos.

Second, 17gph at 31.7/2380 is very close to the book values for peak TIT, and at that high of a power setting the CHTs should be in the neighborhood of 400º. Your hottest CHT shows as 349º, which also seems unlikely because your power setting is right in the middle of the "red box".

Third, as Paul pointed out, your EIS is indicating 65% HP which is definitely incorrect.

The generally accepted "safe" ROP power setting is ~18gph at 29/2400, which nominally yields a TIT in the mid to upper 1500s and CHTS in the high 300s. With that as a baseline, your indications appear suspect.

I'm sure you've spent some time looking at it but I'm including the POH power chart for reference within this thread so others can see what the book says. And we know that we don't want to fly these numbers.

[PilotX]

22/34” 14.5gph (137KIAS @12500) = 170 true