Newbie question - high density altitude takeoff performance

[nikprak]

Hi, I'm a newbie to Diamonds. I plan to get checked out in a 2008 DA40 XLS soon, and was studying the official POH, which from what I have been told, is conservatively generic in terms of the performance charts? I was hoping someone could chime in regarding realistic takeoff climb performance in the following configuration:

2008 DA40 XLS with PF exhaust, two-blade metal Hartzell, 50g tanks.
Density Altitude: 9500 ft
Runway: 8000feet
MTOW
Mixture leaned to to 75F ROP (prior to takeoff roll, at WOT)
Prop at max throughout takeoff climb.
Assume calm winds, and flat surrounding terrain.

Would the above be skirting the boundaries of a safe departure? What would the initial climb rates be like?

Thanks, Nik

[smoss]

I can tell you that sounds close to me and my family leaving Big Bear in the summer, but we are usually shy of MTOW by 150 pounds, and their runway is only 5800 long. Your extra weight would probably put you about similar to my condition. It is very doable, and we do it often, but it does take some getting used to. The acceleration is really slow, you'll think something is wrong until you get used to the feeling. I typically will do a soft field takeoff because if using a typical takeoff, it takes what seems like forever to go from 55 or so to 59 KIAS, and the plane gets very squirrely on the runway during that zone when there for several seconds. Off the runway about midway usually, then in ground effect to say 2/3 the way, then climb from there. The climb is pretty darn slow, about what the POH shows in the chart at about 200-300 fmp max. The climb out in Big Bear is usually over a lake, so have plenty of time to get up, but nonetheless it is disconcerting. Now if there is even a 10 knot headwind for takeoff, it becomes much easier and always seems like a piece of cake.

2007 DA40 XL with PF exhaust, two-blade metal Hartzell, 50g tanks

[Colin]

When I have done that same midday takeoff from Big Bear I head out over the lake bouncing off the top of ground effect (lake effect?) until I have gathered a lot of airspeed. I head to the dam at the far end, because if I need to I could drop over that and follow that valley down to gain more airspeed. 200fpm is what I see on the departure end.

[Rich]

Being at MTOW (2600) is rare for me. ~2600 is about the max I've had, and that on only a couple of occasions. Adding PF added significantly (300+ FPM) to my ROC at SL but I don't have any figures at higher DA, as the highest it's happened to be at takeoff when I've loaded up close to max was a modest 4000-ish ft. DA.

The closest I can come to answering your question is several cases of takeoffs from Rock Springs, WY on July and August afternoons in '04 and '05. Weight around 2300 lbs., both prior to installation of the PF. DA 9000-9500 ft. in all cases. The POH in these cases predicts about 300 FPM and that's what I recall on initial climbout at 70 KIAS. Lean for max RPM in the runup, full throttle if you can. But if it's hot you'll have to increase A/S somewhere on climbout or the CHT's will start to be concerning, thereby costing you ROC.

Typically runways at these elevations are plenty long. The big issue is what you do after leaving the security of the runway behind. Remember your ground speed is significantly higher than indicated in these cases (figure ~80 when showing. 70, e.g.), producing a more shallow climb than the same ROC at lower elevations would produce. And turning costs you ROC.

[Rich]

I typically will do a soft field takeoff because if using a typical takeoff, it takes what seems like forever to go from 55 or so to 59 KIAS, ...

I've also found this to be generally true. I tend to pick the plane off the pavement somewhere around 45-50 KIAS and it seems it's at 60 almost instantly, whereas it takes longer to cover that interval with it still rolling on the ground. (My typical operational field elevation is 3000-5000 DA and 2200-ish pounds).

[nikprak]

Thanks for the feedback guys, much appreciated!