Short field take off

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Bartek
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Re: Short field take off

Post by Bartek »

I am pretty sure approach flaps could reduce the take-off roll significantly.
When needed and used wisely (allowing for Vmc, shallow climb etc.) - why not, it is some better option than ploughing the end of the runway...
However I am interested from the legal perspective - if POH does not say a world about it - is it legal to use such a technique? Common sense says "why not", other planes take-off this way. But what is the legal interpretation of such procedure missing in the POH?
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Re: Short field take off

Post by carym »

In the US this isn't a legal issue. It is only an issue if there is a problem (damage or injury) and insurance won't pay because the NTSB ruled that you flew the plane in a careless and wreckless manor, i.e., didn't follow the procedures outlined in the POH. Often what we do is driven more by what the insurance companies say to us rather than what the FAA says.
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Re: Short field take off

Post by TimS »

Bartek wrote:I am pretty sure approach flaps could reduce the take-off roll significantly.
When needed and used wisely (allowing for Vmc, shallow climb etc.) - why not, it is some better option than ploughing the end of the runway...
However I am interested from the legal perspective - if POH does not say a world about it - is it legal to use such a technique? Common sense says "why not", other planes take-off this way. But what is the legal interpretation of such procedure missing in the POH?
Note, the following is based on what I have read. I am not a lawyer, this is not legal advice, I did not stay at a Holiday Inn last night.... Blah, Blah, Blah...

Under Part 91 in the USA. You are free to do whatever you want. Now, if you crash you may have to defend your position. If you do something as simple as create your own data by "testing" the configuration you have a defensible position from the FAA and likely from your insurance company. The potential "gray" area where you are likely to get sued anyway is the passengers or others that are on the ground.

Tim
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Re: Short field take off

Post by cfiguy »

TimS wrote: Under Part 91 in the USA. You are free to do whatever you want ...
Tim
Tim,

I think you are spot on with regard to careless and reckless operation, but it's important to know what the AFM and part 91 actually says.

I regularly fly a DA42NG and the DA42 TDI (2.0). Taking off with APP flaps is the approved short field procedure for the NG and takeoff performance data is provided. While APP flaps may very well aid takeoff performance in the DA2 TDI, it isn't documented and there is no performance data provided.

14 CFR 91.9 (a) "... no person may operate a civil aircraft without complying with the operating limitations specified in the approved Airplane or Rotorcraft Flight Manual ...

From the DA42 TDI AFM: "This airplane may only be operated in accordance with the procedures and operating limitations of this Airplane Flight Manual."

So saying we are free to do whatever we want would not seem to be supported by either part 91 or the manufacturer.

Just sayin' ...

John
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Re: Short field take off

Post by TimS »

cfiguy wrote:
TimS wrote: Under Part 91 in the USA. You are free to do whatever you want ...
Tim
Tim,

I think you are spot on with regard to careless and reckless operation, but it's important to know what the AFM and part 91 actually says.

I regularly fly a DA42NG and the DA42 TDI (2.0). Taking off with APP flaps is the approved short field procedure for the NG and takeoff performance data is provided. While APP flaps may very well aid takeoff performance in the DA2 TDI, it isn't documented and there is no performance data provided.

14 CFR 91.9 (a) "... no person may operate a civil aircraft without complying with the operating limitations specified in the approved Airplane or Rotorcraft Flight Manual ...

From the DA42 TDI AFM: "This airplane may only be operated in accordance with the procedures and operating limitations of this Airplane Flight Manual."

So saying we are free to do whatever we want would not seem to be supported by either part 91 or the manufacturer.

Just sayin' ...

John
John,

The statement:
"This airplane may only be operated in accordance with the procedures and operating limitations of this Airplane Flight Manual."

is from the DA42 AFM forward. This is not regulatory in nature or approved by the FAA. As such, it has no enforceable action or requirements.

The critical section which applies is section (2) Limitations; and this section must be approved by the FAA. You will not see anything in section 2 about takeoff procedures.

Tim
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Re: Short field take off

Post by cfiguy »

TimS wrote: The statement:
"This airplane may only be operated in accordance with the procedures and operating limitations of this Airplane Flight Manual."

is from the DA42 AFM forward. This is not regulatory in nature or approved by the FAA. As such, it has no enforceable action or requirements.

The critical section which applies is section (2) Limitations; and this section must be approved by the FAA. You will not see anything in section 2 about takeoff procedures.
Tim,

As you said, you are not a lawyer. Neither am I.

My litmus test is to take any regulatory interpretation I concoct and preface it with "Your honor ..." I think we'll have to agree to disagree on this one.

John
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Re: Short field take off

Post by CFIDave »

John:
As Tim noted, only the Operating Limitations listed in Chapter 2 of the POH/AFM are regulatory. If you look at the table of contents, you'll see that all the other chapters are "(a non-approved chapter)."

Since there's nothing in chapter 2 about takeoff procedures, from a regulatory standpoint you're legally able to use APP flaps for takeoff. However as we're commonly reminded when flying, "what's legal isn't necessarily safe." An example would be trying to take off with LDG flaps. So ultimately it's up to the PIC to exercise good judgment.
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Steve D
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Re: Short field take off

Post by Steve D »

Hi

Back from the bush and my little 'experiment". I can report that at normal take off trim setting, the aircraft rotates with a small amount of back pressure on the stick and leaps into the air with what I could best describe as alacrity. :D This happened at 64kts. but I am sure you could get it unstuck at lower numbers if required. The takeoff roll was dramatically shortened which was my main aim. Unfortunately I cannot give a definitive answer on how much shorter but estimate at least 100m, possibly more. This is a big number when the P.O.H. records ground roll as 427m.

Once airborne, I allowed the aircraft it to climb about 50ft, then leveled out and accelerated to blue line which happened completely normally. There was no perceptible lag in the time taken to get to blue line but logic dictates this must be a little longer. Cleaning up and flying away was a non-event. The takeoff was conducted at 4,500ft a.m.s.l. and I.S.A.+12. We were +/-20kgs light of M.A.U.W.

Having performed the maneuver, I am confident that there are few extra risks over a normal takeoff. The aircraft felt completely normal with no excessive stick forces to contend with. I cannot comment on the legality issues but would like to know why it was never included in the P.O.H. The ex-CEO of Diamond recommended it as perfectly acceptable method to reduce takeoff roll but I did not think to ask him why it wasn't in the P.O.H. as an approved practice.
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Re: Short field take off

Post by carym »

Steve,
Thanks for the info. Performing a "short field take off" always involves a little more risk than normal procedures. It's speculation on my part, but I suspect that rotation (64 KIAS) 18 kts below blue line is probably why they didn't want to "certify" this procedure in the POH. It is good to know that this works well if and when it is really needed.

In general I try to avoid runways under 2700 feet for fear of what may happen if I lost an engine just after rotation. There is an airport (KMIC) near where I used to be based whose longesst runways are 3250 feet. The trees and houses just off the end of the runway are a sure target if an engine went out and departing that airport during a hot summer day always raised the pucker factor for me. The runways where my maintainence was done (21D) on my C310 were 2500 and 2800, and they were much less of a concern because there was plenty of room away from houses beyond the runway ends. The decision as to how to depart is always more complicated than just the runway length.
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Re: Short field take off

Post by cfiguy »

Another option to consider is installing a Microair vortex generator kit. One DA42 I fly has these installed and they definitely seem to help. The manufacturer claims Vmc and stall speeds are all reduced. I'm not sure they help as much with takeoff as they do on landing.

John
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