Socata Reviews ?
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What is the fuel flow in your Mooney at say 140kt IAS? I get 10.5 GPH (USG).
It should be lower because a Mooney has a narrower cockpit; the frontal area of a plane is a major thing in fuel efficiency. A Spitfire is even more narrow
It should be lower because a Mooney has a narrower cockpit; the frontal area of a plane is a major thing in fuel efficiency. A Spitfire is even more narrow
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Originally Posted by IO540
What is the fuel flow in your Mooney at say 140kt IAS? I get 10.5 GPH (USG).
Generally I cruise at 2400 rpm a little richer than 100F ROP for a fuel burn around 9.7 USG/hr and a TAS of 154-156. I do keep an occasional log of real-world parameters so I can track any long-term changes in temps, pressures, speeds etc, but I've only recently added the fuel burn. Looking at that, the only times I've flown that slow and noted the fuel flow have been LOP operations, which probably aren't the numbers you're interested in. All the same:
137kts at FL100 burning 7.9 USG/hr (29.9 lit/hr)
135kts at FL100 burning 7.7 USG/hr (29.1 lit/hr)
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Oh, sorry - just re-read your message. Those are TASs quoted above, not IASs.
The nearest IAS numbers I've got on my log are:
- IAS 135, TAS 156, FL100 for a fuel flow of 9.7 USG/hr (36.7 lit/hr)
The nearest IAS numbers I've got on my log are:
- IAS 135, TAS 156, FL100 for a fuel flow of 9.7 USG/hr (36.7 lit/hr)
Last edited by Wrong Stuff; 19th Aug 2006 at 08:15.
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Originally Posted by Wrong Stuff
In reality with the J, the gear doors are very close to the ground and could easily get damaged.
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You fell into the aeroplane salesman IAS/TAS trap there
At FL100, 138kt IAS is about 155kt TAS. So you are 9.7GPH, I am 10.5 GPH. That is an 8% difference; probably accounted for by the difference in the cockpit frontal cross-section alone. You pays your money and you takes your choice, and width matters more than length in this case
I wonder why your LOP figures are so much slower. The fuel flow doesn't have to be that much lower. There is no efficiency gain in going that far LOP. The tiniest amount past peak EGT is every bit as good. Perhaps you cruise at 75% or higher power.
The thing that you pay for heavily is flying at max cruise, versus flying just a bit under. I get the impression that a lot of Americans fly at 75%, and well rich of peak. Hence the old saying that fuel is the cheapest thing you can stick inside your engine. Less and less true every day, but it undermines the decades-old preconceptions about some planes being more efficient. It also makes comparisons of different planes' cruise performance, from published data, nearly impossible.
Pianorak - there are grass strips and there are grass strips. Some are perfectly OK, e.g. Panshanger. Many are dreadful, with potholes which the owner would not tolerate in his back garden, but if somebody bends their plane on his airfield he sticks his finger up and tells them to claim off their insurance. My view is that grass is OK for any of the TB series, but it's true for all planes that operating from grass will result in higher operating costs in the long run, as well as a generally filthier plane all round.
A TB20 with a 3B prop has 8" of ground clearance on the prop. The front gear suspension travel is 3" (probably same for all TBs, old and new) which leaves 5" max allowable pothole depth. However, this 5" can be exhausted if the ground ahead is rapidly rising, as often is the case on grass-concrete transitions. One must have a walk-around before departure, always, to make sure one can taxi away, and use the towbar if necessary. Even if this p1sses off a queue of renters behind.
At FL100, 138kt IAS is about 155kt TAS. So you are 9.7GPH, I am 10.5 GPH. That is an 8% difference; probably accounted for by the difference in the cockpit frontal cross-section alone. You pays your money and you takes your choice, and width matters more than length in this case
I wonder why your LOP figures are so much slower. The fuel flow doesn't have to be that much lower. There is no efficiency gain in going that far LOP. The tiniest amount past peak EGT is every bit as good. Perhaps you cruise at 75% or higher power.
The thing that you pay for heavily is flying at max cruise, versus flying just a bit under. I get the impression that a lot of Americans fly at 75%, and well rich of peak. Hence the old saying that fuel is the cheapest thing you can stick inside your engine. Less and less true every day, but it undermines the decades-old preconceptions about some planes being more efficient. It also makes comparisons of different planes' cruise performance, from published data, nearly impossible.
Pianorak - there are grass strips and there are grass strips. Some are perfectly OK, e.g. Panshanger. Many are dreadful, with potholes which the owner would not tolerate in his back garden, but if somebody bends their plane on his airfield he sticks his finger up and tells them to claim off their insurance. My view is that grass is OK for any of the TB series, but it's true for all planes that operating from grass will result in higher operating costs in the long run, as well as a generally filthier plane all round.
A TB20 with a 3B prop has 8" of ground clearance on the prop. The front gear suspension travel is 3" (probably same for all TBs, old and new) which leaves 5" max allowable pothole depth. However, this 5" can be exhausted if the ground ahead is rapidly rising, as often is the case on grass-concrete transitions. One must have a walk-around before departure, always, to make sure one can taxi away, and use the towbar if necessary. Even if this p1sses off a queue of renters behind.
Last edited by IO540; 19th Aug 2006 at 08:45.
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Originally Posted by Pianorak
The same presumably applies to a M20F.
Originally Posted by IO540
I wonder why your LOP figures are so much slower. The fuel flow doesn't have to be that much lower. There is no efficiency gain in going that far LOP. The tiniest amount past peak EGT is every bit as good. Perhaps you cruise at 75% or higher power.
Although LOP does give lower CHTs, they're never that high to begin with. At 100 ROP the hottest cylinder never goes above 360F, which is fine. At 25 LOP the CHT falls to around 290F. And LOP does give lower fuel burn, but again it's not that high to begin with, so the saving in relation to the speed loss doesn't seem worth it.
The late Roy LoPresti who designed the M20J had a motto - "Life is short - Fly FAST!" It seems disrespectful to his memory to fly a Mooney at anything less than full chat.
