Which Manufacturers Performance Numbers Do You Trust

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pelmet
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Which Manufacturers Performance Numbers Do You Trust

Post by pelmet »

I don't mean to compare between different manufacturers. I mean comparing between different divisions of the same manufacturer.

Of course this is all based on a simple post that I read on another forum and subject to error but this is what he said......

"I have a 65 Bonanza. The original 1965 AFM (Airplane Flight Manual) was right on. Beech issued a revised complete POH around 1980. The numbers in it are 200 to 250 feet optimistic. I guess the Sales dep't has more say than engineering."

Beware of the performance numbers anyway....you never know if it took ten attempts by the test pilot to get the best performance number used in your manual.
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PilotDAR
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Re: Which Manufacturers Performance Numbers Do You Trust

Post by PilotDAR »

Look in the front cover of the document you're reading from: Is it a approved Flight Manual? Or, is it a POH/Owner's Manual, or Information Manual. Different planes have different documents, and some have more than one. I know that some Pipers have both an "Owner's Handbook" and an FAA approved Flight Manual. They have different contents. I recall which test flying a Twin Comanche, that the Owner's Handbook climb performance values were amazingly optimistic. My mentor suggested that I check the FAA approved Flight Manual for the plane. Huh? There's more than one pilot document? Yes, there is. The FAA approved Flight Manual for the Twin Comanche is not glossy, and does not contain climb data, as it is not required to be provided to the pilot for that certification basis plane. So, if you're referring to the "Owner's Handbook" for a a Twin Comanche (and other Pipers), what you're reading is not FAA approved, and of un proven origin. For other types, (Some Cessnas), you may find a statement in the front of the "Pilot's Operating Handbook" which describes its relationship the flight manual - like it meets that requirement. Airplanes from the '60's and earlier may not follow this format, and that's just the way it is.

What you'd like to read is "FAA Approved", then you know that any information provided in Section 2, Limitations, 3, Emergency, 4 normal Procedures, or 5, Performance is actually FAA approved, and accurate. If you have an FAA/TC/EASA approved Flight Manual, any performance data presented will be accurate, as it has come from flight testing results which have been verified - I've done the testing.

I have generally found Cessna performance data to be quite accurate. I have found Piper "Owner's Handbook" data to be optimistic!
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pelmet
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Re: Which Manufacturers Performance Numbers Do You Trust

Post by pelmet »

Thanks,

Once again, this is just a quote from that same thread, so no proof. But.....

"Cessna used to take two test pilot runs as an average, other manufactures used the worst run of the test pilots, others added 2-3% safety margin."

Keep in mind that there are many aircraft out there that are not certified. Who knows what their procedure is for performance numbers.
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Big Pistons Forever
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Re: Which Manufacturers Performance Numbers Do You Trust

Post by Big Pistons Forever »

Cruise speed and range figures seem to me to be the most optimistic. I don"t think I have ever seen a piston powered airplane give me the book TAS

Also don't forget the average light airplane is 40 + years old so it is unlikely to perform as well as it did new
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photofly
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Re: Which Manufacturers Performance Numbers Do You Trust

Post by photofly »

If your tach is 50rpm off you won’t get the expected cruise speeds. And if the plane came equipped with wheel pants and they’re not installed on the airplane you fly that will cost you a few knots too.

If you’re looking at rate of climb, 1000 feet of indicated altitude in the summer is bigger than 1000 feet of indicated altitude in the winter. And wind gradients have a big effect on climb rates.

I do remain skeptical ask that aircraft age has much to do with it. Engines should produce rated power if the cam lobes aren’t worn, and ignition and fuel systems are correctly set up; if they’re not they should get fixed. And old aircraft have engines that are often decades younger. Aircraft rigging issues? Perhaps. Dirty airplane? You should probably clean it before making any measurements.
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