Newbie Question 1 - Flaps UP takeoff

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ememic99
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Re: Newbie Question 1 - Flaps UP takeoff

Post by ememic99 »

CFIDave wrote: Mon Mar 06, 2023 1:41 pm T/O flaps can optionally be used on DA42 NG/-VI models for short-field takeoffs.
It's the same for CD-155 equipped DA42 TDI.
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Re: Newbie Question 1 - Flaps UP takeoff

Post by photoSteveZ »

CFIDave wrote: Mon Mar 06, 2023 1:41 pm FWIW, the DA42 does not normally use 1/2 flaps on takeoff, which is why on the DA42 they're labeled "APP (Approach Flaps)" rather than "T/O (Takeoff Flaps)" on that aircraft. (T/O flaps can optionally be used on DA42 NG/-VI models for short-field takeoffs.)

In contrast, Diamond chose to label 1/2 flaps as Takeoff Flaps on the DA62 (and DA40). In DA62 transition training, I teach that pilots should couple T/O flaps with the Electric Fuel Pumps ON: For takeoffs and landings, whenever you turn fuel pumps ON, you also set T/O flaps; you turn Electric Fuel Pumps OFF when you raise the T/O flaps to flaps UP -- it makes it easier to remember both.

In flying the DA62, I've noticed that (particularly when heavy) I sometimes hear the stall warning horn chirp momentarily when rotating off the runway without use of T/O flaps, whereas I don't hear the horn sound when using T/O flaps.

Bottom line, I'd suggest setting T/O flaps for DA62 takeoffs.
I’m with you, Dave. Based on the discussion here, I decided to try a no-flaps takeoff yesterday and was surprised at the significantly higher back stick force required to rotate. The solution would be to set the pitch trim more nose-up than I do for Flaps1 takeoffs, of course. The stall warning horn chirped a couple of times in the initial climb out in modestly turbulent conditions and the plane felt just a bit less solid. I see no particular advantage to no-flaps takeoffs and will go back to using Flaps1.
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Re: Newbie Question 1 - Flaps UP takeoff

Post by CFIDave »

One more consideration that suggests using DA62 T/O flaps: Vmca with T/O flaps is 70 knots, whereas Vmca with flaps UP is 76 knots -- a huge 6 knot difference that could be significant if you were to lose an engine on takeoff.
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Re: Newbie Question 1 - Flaps UP takeoff

Post by Boatguy »

I consulted with a seasoned and very knowledgable DA62 CFI who does not participate in DAN who largely agreed with Dave. His SOP is to use flaps TO. The reasons were:

- The most critical thing for EFATO in a twin is maintaining directional control which is made easier by the 6kt reduction in Vmc.

- He values a shorter ground roll, which reduces accelerate stop distance, and a little more room to put the plane back on the runway, more than the reduction in distance over 50', based on the airports from which he would expect a DA62 to operate.

He also directed me to this video of Diamond doing EFATO testing in a DA42.

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Re: Newbie Question 1 - Flaps UP takeoff

Post by mfdutra »

And what speed do you guys rotate? My factory instructor suggested waiting until Vyse if there's runway available.
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Re: Newbie Question 1 - Flaps UP takeoff

Post by CFIDave »

To keep it simple, I use 78 knots with T/O flaps for rotation, regardless of weight.

IMHO, excess altitude is better than extra speed during takeoff, so that's why I don't wait until Vyse to rotate. You can always trade off speed vs altitude using pitch, but since drag increases with the square of velocity, more altitude lets you maintain more potential energy in case you lose an engine. So unlike some pilots, I don't let the plane accelerate in ground effect and then do a zoom climb after reaching end of the runway.
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Re: Newbie Question 1 - Flaps UP takeoff

Post by greg »

Boatguy wrote: Sat Mar 11, 2023 7:45 pm He also directed me to this video of Diamond doing EFATO testing in a DA42.

https://www.youtube.com/watch?v=RQeBHSsL56o
Sorry for another newbie question (I’ve never flown a twin), but was the test pilot cheating by always starting the take off run well to the right of centreline? Most of the landings were to the left of centerline (on a very wide runway). Had the runway been narrower it would have landed on the grass.
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Re: Newbie Question 1 - Flaps UP takeoff

Post by mfdutra »

greg wrote: Tue Mar 14, 2023 8:06 pm was the test pilot cheating by always starting the take off run well to the right of centreline?
I don't think so. You do that for the safety for the test itself. No different than us being 3000+ AGL when doing stalls, etc.

The test was always cutting the left engine. You don't want to give up safety margin and risk damaging the airplane.
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Re: Newbie Question 1 - Flaps UP takeoff

Post by Boatguy »

This was filmed through a very wide angle lens, probably a GoPro as it looks like a familiar angle. If it's the airport at Wiener Neustadt, it's only 1,067m (3,500') so probably 25m wide. He clearly starts off on the right side, and when the engine fails the plane immediately yaws left, then the pilot banks right, as expected. The plane could have continued the TO as he does in the simulated failure at 50', but obviously he chooses to land in the other examples and comes back towards the centerline, but not always on the center.

Yes, the pilot could have been more careful to land on the centerline, but in no case would he have had to land on the grass.
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Re: Newbie Question 1 - Flaps UP takeoff

Post by nworthin »

Boatguy wrote: Sat Mar 11, 2023 7:45 pm I consulted with a seasoned and very knowledgable DA62 CFI who does not participate in DAN who largely agreed with Dave. His SOP is to use flaps TO. The reasons were:

- The most critical thing for EFATO in a twin is maintaining directional control which is made easier by the 6kt reduction in Vmc.

- He values a shorter ground roll, which reduces accelerate stop distance, and a little more room to put the plane back on the runway, more than the reduction in distance over 50', based on the airports from which he would expect a DA62 to operate.

He also directed me to this video of Diamond doing EFATO testing in a DA42.

https://www.youtube.com/watch?v=RQeBHSsL56o
Looks to me that all these tests in the video were done in in the DA42 Flaps UP position. Since this is the *only* authorized take off procedure (except for short field) in the DA42 NG AFM this makes sense.

Comparing that standard procedure to that of the DA62 where both a Flaps UP or Flaps T/O procedure are both documented as "standard" is Apples to Oranges.

And to the extent that one might surmise that the DA62 would fly like the DA42 in a "right after take off OEI" scenario, this video seems to argue for the Flaps UP take off procedure for the DA62.

Note that, except for that last test (where the take off was continued after failure), all examples demonstrated the benign characteristics of the DA42 losing the critical engine (with flaps up) and continuing to land (on a runway long enough to allow for this). This probably applies to the DA62 as well. So, by that logic, if you think you are going to lose one at 50ft or less on a long runway in your DA62, take off with flaps UP.

But what if the runway *isn't long enough to land on* after the engine quits? In that case, you want to be in the configuration that allows for best climb (or at least not drift down) flying single engine. In the DA62, the performance charts are very clear: that's gear and flaps up. So, by that logic, take off with your DA62 (with correct technique) with flaps UP in that case too.

I'm just not sure my piloting skills or cognitive recognition skills are great enough to react to loss of engine power and go through the extra steps to get the plane in the optimal configuration if taking off with T/O flaps deployed. If I'm on a long runway (particularly one with limited landing spots immediately off field), I would much rather make sure the airspeed is on the high side of 80 kts, rotate slowly, gather some climb rate and get the gear sucked up ASAP after observed positive rate. And do this with flaps UP. Because if I lose one then, it's a much simpler scenario - In fact it's just like what was seen in the DA42 video.

I get that if the DA62 pilot is ham handed and pulls up early, and/or climbs at a high initial AOA with flaps UP and then loses an engine, this is not good. But to my mind, unless I am actually on a short field, being mindful about speeds (i.e. solidly aboe Vr and well above Vmca thereafter) with good technique (moderate climb attitude) on take off using flaps UP (a fully authorized procedure from Diamond) this seems to me minimizes the downstream risks the most if I do lose one in this critical regime of flight.

None of this logic applies on a 3000 foot runway, in the summer, fully loaded, where there's no obstructions on the departure end. As the best instructor I ever learned from was fond of saying, it depends.
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