160 KTAS on SR20

Guest Discussion
1

I’m still working on how to get close to 160 KTAS on my SR20. Beyond keeping it clean, and keeping the CG aft, here’s my question:

According to the POH cruise performance tables, in no case does the plane make 160 without either 2700RPM or power higher than 75%. My understanding was that cruise should be at 75% power or less, and RPM should be at 2500. Now, I’m thinking that my understanding may be wrong.

For example, at 6000 feet / ISA, is it okay to do 24"/2700RPM, which is 83% power and 163KTAS? How about 8,000 feet /ISA 22.2"/2700RPM?

Upon looking at this, I’m beginning to believe that my lackluster speeds may have been self-inflicted.

Appreciate any input.

Andy

2

Andy,
I believe that with FULL throttle in 8000 ft on an ISA standard day (minus 1 degree Celsius, 29.92 QNH) you should achieve something between 155 and 160 KT TAS, as indicated on the temperature correction card of the Airspeed indicator, or GS on a calm day. If you still have less, then something is wrong.

Regards,

Timm Preusser N747TG

3

With this engine config and best conditions, most will peak between 5000-6000 feet. Above that the reduction in drag / increase in TAS is not going to keep up with loss of engine power. I think the power curve is near 6500.

4

For example, at 6000 feet / ISA, is it okay to do 24"/2700RPM, which is 83% power and 163KTAS? How about 8,000 feet /ISA 22.2"/2700RPM?

Yes, but…

The POH says that above 75% power you must keep the mixture fuel rich, so your 160KTAS will come at a high fuel flow rate.

Optimum altitude is around 8000’ - i.e. the level at which you can keep the power lever full forward for 2700rpm and the power will be at 75% or less.

The SR20 engine is rated to operate at full power continuously, so you could fly around all day at any altitude with the power lever full forwards if you observe the rules about leaning. Just don’t expect long range or low fuel bills.

5

How does weight figure in? At 2500 vs. 2900?

6

400!

7

SR20 cruise performance figures are calculated at 2500 lbs. In my experience, full gross weight of 2900 lbs. costs at least 4 knots off speeds at the lighter weight.

8

400

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9

A Good Sense of Humor is ALWAYS Welcome

10

Thanks! That’s exactly the issue and the information I was seeking.