DA42 TDI Max Airspeed

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JimB

DA42 TDI Max Airspeed

Post by JimB »

I am considering buying a DA42 under the Certified Pre Owned program. It will have new Continental 2.0 engines, but otherwise will be identical to DA42 TDI. Performance should be identical.

All the airspeeds I have seen published are at 70% power.

What true airspeeds would I expect to see at higher power settings (90%, 100%) at non-oxygen altitudes (8,000 or 10,000 MSL)?

Are there any disadvantages to operating at higher power settings other then higher fuel flow?

Thanks!
Jim
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jon1746
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Re: DA42 TDI Max Airspeed

Post by jon1746 »

This is my normal mission profile. I went through the process in 2013. I see 155 at 80% in the 9 - 10 range. 160 if I get up to the high teens.
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carym
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Re: DA42 TDI Max Airspeed

Post by carym »

jon1746 wrote:This is my normal mission profile. I went through the process in 2013. I see 155 at 80% in the 9 - 10 range. 160 if I get up to the high teens.
That is about right. The POH for this plane is available and the published TAS in the POH is very accurate. I always flew at 75% power and got about 150 KTAS at 8-10K and 155 KTAS at 14K. Because the manufacturer (Thielert) recommended 70% power for cruise, I was reluctant to use higher power settings. FWIW, I had the 1.7 engines and never had a problem with the piston cooling nozzles or any other issue with my engines through the 900 hours I had the plane.
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Re: DA42 TDI Max Airspeed

Post by Doug »

I have seen 170 at upper teens..
150 to 160 below 10K is doable.
I had the 2.0L and found that everything timed out before it wore out so I usually ran 80 - 90% HP
170
170
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Re: DA42 TDI Max Airspeed

Post by carym »

Doug,
I know that running beyond TBR (or TBO) is somewhat controversial, but in the US if the plane is not operated for commercial purposes, one can continue to deem the airplane as airworthy even beyond TBR. That is why, in part, I felt compelled to keep the power down to about 75% in cruise. Even though I had to add oil about every 7-8 hours, my engines continued to meet the compression standards. There have been 1.7 engines that went beyond 2000 hours with only clutch and gear replacements at the 300 hour intervals. Are you required to replace the engines at TBR in Canada if the planes are used for personal purposes only? At >$120,000 for engine replacements, it adds more than $120/hour for engine reserves.
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JimB

Re: DA42 TDI Max Airspeed

Post by JimB »

Thank you. Appreciate the info. -Jim
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Re: DA42 TDI Max Airspeed

Post by CFIDave »

I my experience a 2.0L Thielert-powered DA42 (now Continental CD-135) has a top cruise airspeed of approximately 160 knots TAS at non-O2 altitudes of 11-12,000 feet.

And to Cary's point about operating DA42 engines past TBR: There is a 2.0L Thielert DA42 with a local flight school based here at KJYO that is operating well past TBR with no problems; it's flown regularly. As long as it continues to pass annual and 100-hour inspections (required for flight-school rentals) with good compressions and the engines aren't making metal, it's perfectly legal to fly in the US.
Last edited by CFIDave on Tue Aug 30, 2016 1:20 pm, edited 1 time in total.
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Re: DA42 TDI Max Airspeed

Post by Doug »

carym wrote:Doug,
I know that running beyond TBR (or TBO) is somewhat controversial, but in the US if the plane is not operated for commercial purposes, one can continue to deem the airplane as airworthy even beyond TBR. That is why, in part, I felt compelled to keep the power down to about 75% in cruise. Even though I had to add oil about every 7-8 hours, my engines continued to meet the compression standards. There have been 1.7 engines that went beyond 2000 hours with only clutch and gear replacements at the 300 hour intervals. Are you required to replace the engines at TBR in Canada if the planes are used for personal purposes only? At >$120,000 for engine replacements, it adds more than $120/hour for engine reserves.
Sorry if I can out as disagreeing with your decision to run at 75%, it was not my intention. I felt that the 2.0L engines have had very good reliability and running a higher % HP worked well for me. I did run in the 70% range from time to time when I was early or trying to stretch fuel range and it was very relaxing. Less noise and slightly smoother.
Back to your question regarding TBR, it is also a grey area in Canada for private operators. Since I covered extra miles per engine hour by running a higher % HP by cost per mile was less. Since I use aviation mainly for business purposes my plan was to follow the TBR spec.
Doug Thompson
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