Carson speed

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Trigger
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Carson speed

Post by Trigger »

Hi guys, I am new at the forum but I've been following it for a while.
As Diamond doesn't provide best glide to "compute" Carson Speed, based on your experience what you be the speed (and power settings) for a very long flight (around 1000 NM).
I've made some trials and I figure out that L/Dmax is around 90/95 Kias meaning (according Carson speed) best range speed will be around 118/125 Kias (35/40% power setting). Does this makes any sense?
Thanks
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Re: Carson speed

Post by dgger »

My gut feeling and some preliminary measurements in a DA42NG, which I took for an Atlantic crossing, suggest it is a bit higher than 35/40% - at least, if you're anywhere near MTOM.

I found that airspeed fluctuation increase significantly when pulling back, so getting good measurements was a bit of a challenge. Nevertheless, at MTOM (1,900kg in my case) 45% gave me a clear improvement in range over 50%. Lower than that yielded mixed results. My speeds were a bit different, though. At 45% I get about 125-ish KTAS at 10,000ft IIRC.

The most interesting data point I could find so far was this: http://www.diamond-air.at/en/media-cent ... -non-stop/. Apparently, you get best range in a TDI at 42% ;)
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Re: Carson speed

Post by ememic99 »

dgger wrote:Apparently, you get best range in a TDI at 42% ;)
From article: "Guillaumaud set engine power at a fuel conserving 42% and achieved an average ground speed of 152 kts."
Original TDI with 42% hardly can achieve 152 kts of TAS (at 10.000 feet you need around 70% to achieve that) - obviously heavy tailwind was involved in this crossing :) And 42% yields 3 GPH per engine a bit more than stated.
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Re: Carson speed

Post by dgger »

ememic99 wrote:Original TDI with 42% hardly can achieve 152 kts of TAS (at 10.000 feet you need around 70% to achieve that) - obviously heavy tailwind was involved in this crossing :) And 42% yields 3 GPH per engine a bit more than stated.
According to the POH 50% in ISA conditions at 10,000ft should be give you 127 KTAS. I would assume they easily had 40 knots average (!) tailwind. That's the way to go for your 1000NM leg. But pray for the weatherman to be infallible...

The reason I mentioned the press release is not because of the accurate data, but because pilot for the PR stunt with the assumed backing of the Diamond engineering team deliberately chose 42% - which for the prevailing condition I take to be the best available choice i.e. the maximum range speed that OP had asked for.
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Re: Carson speed

Post by ememic99 »

It really requires patience to fly 125 kts in aircraft that easily can do 50 kts faster :)
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Re: Carson speed

Post by dgger »

Sure does. However, the upside of not having to use a raft has been a sufficiently strong incentive on my longer legs.
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Re: Carson speed

Post by robert63 »

The Gyronimo App for the DA42NG gives the best range at 18.000 ft with 50% power setting. The range at ISA and 0 wind is 1.119 NM. Speed is 142 KTAS at 8.7 Gal/h. The 30 Minutes reserve is not included. The App is quite accurate for our aircraft.
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Re: Carson speed

Post by Henrik »

dgger wrote:My gut feeling and some preliminary measurements in a DA42NG, which I took for an Atlantic crossing, suggest it is a bit higher than 35/40% - at least, if you're anywhere near MTOM.
Agree completely - I've experimented quite a bit as well (in a -VI) & also feel that around 45% at FL180 is the sweet spot for max range.

You can drop it down below 40%, but the high angle of attack give the airframe a sluggish feel & you feel a tendency of continuously chasing small up & down drafts, which surely can't be efficient. 35% power is really for max endurance & not range.
dgger wrote:The most interesting data point I could find so far was this: http://www.diamond-air.at/en/media-cent ... -non-stop/. Apparently, you get best range in a TDI at 42% ;)
Also they used a 26 gal ferry tank. Impressive distances none the less.
ememic99 wrote:It really requires patience to fly 125 kts in aircraft that easily can do 50 kts faster
Yeah. I generally don't mind long flights. But needing to *deliberately* fly 30-35 kts "slower" for 6 hrs gets kinda old after having done it many times. If you need frequent 1100 nm non-stops, the DA42 is just not the ideal plane. Those missions brings you into M600 territory.
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Re: Carson speed

Post by ememic99 »

robert63 wrote:The Gyronimo App for the DA42NG gives the best range at 18.000 ft with 50% power setting. The range at ISA and 0 wind is 1.119 NM. Speed is 142 KTAS at 8.7 Gal/h. The 30 Minutes reserve is not included. The App is quite accurate for our aircraft.
For this FF (8.7 GPH for both engines) at 18.000 ft TDI achives these numbers (recorded during 500 hours with CD-135 and 100 hours with CD-155):
- CD-135 - 60% load, 142 KTAS, 1247 NM
- CD-155 - 52% load, 146 KTAS, 1282 NM

Zero fuel distances were not measured :) those are only calculations.
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Re: Carson speed

Post by ememic99 »

Henrik wrote:If you need frequent 1100 nm non-stops, the DA42 is just not the ideal plane. Those missions brings you into M600 territory.
Fully agree and that's why I'm trying to limit my legs to 800 NM, flying at 70-75% load which gives 169-174 KTAS at FL180 and FF 12.0-13.2 GPH (the engines are CD-155).
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