DA40 Climb Rate

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DiamondMike
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DA40 Climb Rate

Post by DiamondMike »

Has anyone noticed that the climb rate with takeoff flaps is greater than the climb rate with cruise flaps?

Just looking at the climb performance charts, with the examples shown, you can see a 110 ft/min better climb rate with takeoff flaps over climb with cruise flaps.

Can anyone offer a technical explanation for this performance difference?

Mystery for me. I always thought Vy, best rate of climb speed, would be obtained in the clean configuration.

Performance engineers, aerodynamics experts, others: input welcome.

Thanks.
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Rich
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Re: DA40 Climb Rate

Post by Rich »

I have noticed that. But I think there is an obvious error in the RPM setting for T/O climb. In reality, you have RPM at max (2700) at takeoff, not 2400. I certainly do until well after leaving the runway.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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nathanda40
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Re: DA40 Climb Rate

Post by nathanda40 »

DiamondMike wrote: Sat Jul 09, 2022 9:57 pm Has anyone noticed that the climb rate with takeoff flaps is greater than the climb rate with cruise flaps?

Just looking at the climb performance charts, with the examples shown, you can see a 110 ft/min better climb rate with takeoff flaps over climb with cruise flaps.

Can anyone offer a technical explanation for this performance difference?

Mystery for me. I always thought Vy, best rate of climb speed, would be obtained in the clean configuration.

Performance engineers, aerodynamics experts, others: input welcome.

Thanks.
i have noticed this as well and for a short field situation leave the t/o flaps out until well clear. there's no way that this configuration is more efficient than retracted flaps and i could see that as you climb and need more pitch to maintain the advantage you have at lower altitudes goes away?
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Rich
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Re: DA40 Climb Rate

Post by Rich »

Just assume that the T/O chart RPM should be 2700 RPM (which it will be in the real world) and a great peace will be visited upon you. 8-)
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DaveS1900
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Re: DA40 Climb Rate

Post by DaveS1900 »

Flaps provide two things: lift and drag. When the flaps are in the first notch there is extra lift with not much drag penalty. The extra lift is because the flap makes the wing chord longer (it also changes the angle of attack).

On takeoff (with the first notch of flaps) you are making more lift than than with the flaps up. This also has the effect of lowering your stall speed, which increases the margin of safety.

You might say if one notch is good, full flaps should be better. However, there is a point where the flap angle creates more drag than lift. So it becomes detrimental to a climb. Full flaps are good for landing, but in a go-around you have to get them up to at least the first notch or it hurts the climb.

Dave S.
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DiamondMike wrote: Sat Jul 09, 2022 9:57 pm Has anyone noticed that the climb rate with takeoff flaps is greater than the climb rate with cruise flaps?

Just looking at the climb performance charts, with the examples shown, you can see a 110 ft/min better climb rate with takeoff flaps over climb with cruise flaps.

Can anyone offer a technical explanation for this performance difference?

Mystery for me. I always thought Vy, best rate of climb speed, would be obtained in the clean configuration.

Performance engineers, aerodynamics experts, others: input welcome.

Thanks.
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Re: DA40 Climb Rate

Post by DiamondMike »

“I have noticed that. But I think there is an obvious error in the RPM setting for T/O climb. In reality, you have RPM at max (2700) at takeoff, not 2400. I certainly do until well after leaving the runway.”

Rich, that can be the only explanation.

The takeoff climb chart with flaps takeoff could only be presented with RPM 2700.

The cruise climb chart with flaps cruise is with 2400 RPM.

So I call it a typographical error in the POH. Page 5-13. Should state, RPM lever…..2700 RPM. (In my opinion)

Thanks.
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Rich
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Re: DA40 Climb Rate

Post by Rich »

A data point from today, maybe 40 seconds after liftoff:
Alt 4000 ft
OAT 23 degC
Weight 2200-ish lbs
WOT/2700 RPM
Flaps UP
KIAS 70
Leaned a bit from full rich.

ROC from the chart in the POH: ~680 fpm (w/TO flaps and 60 KIAS)
Actual steady ROC: 1200 fpm

Atmosphere was sinking air if anything, so no boost there

My normal procedure is to retract flaps shortly after liftoff and climb with max available power for the first minute or two and then go to a cruise climb.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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hifiaudio2
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Re: DA40 Climb Rate

Post by hifiaudio2 »

I know this thread has been discussing the gas da40, but what is the common ROC you guys are seeing from the NG? My school indicated that another NG in their fleet (no AC) was getting in the 1200 range while mine, with AC, is getting 600 or less. Is it possible for an NG to climb that fast, and if so, should I be concerned that something other than the AC weight on mine is preventing me from attaining better numbers?
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Rich
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Re: DA40 Climb Rate

Post by Rich »

hifiaudio2 wrote: Tue Aug 16, 2022 5:35 pm I know this thread has been discussing the gas da40, but what is the common ROC you guys are seeing from the NG? My school indicated that another NG in their fleet (no AC) was getting in the 1200 range while mine, with AC, is getting 600 or less. Is it possible for an NG to climb that fast, and if so, should I be concerned that something other than the AC weight on mine is preventing me from attaining better numbers?
Could it be that other plane is using 100% power? The performance charts all are at 92% power and there is no documented weight/altitude wherein climb rate would come anywhere near 1200 FPM. I would also try checking some FlightAware data for this plane and see if that 1200 FPM also shows up there. I check my numbers against FA from time to time, as I routinely beat book numbers substantially and validate against outside sources. In my case (and most other DA40-180s) there are good explanations for this situation.
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Re: DA40 Climb Rate

Post by Boatguy »

hifiaudio2 wrote: Tue Aug 16, 2022 5:35 pm I know this thread has been discussing the gas da40, but what is the common ROC you guys are seeing from the NG? My school indicated that another NG in their fleet (no AC) was getting in the 1200 range while mine, with AC, is getting 600 or less. Is it possible for an NG to climb that fast, and if so, should I be concerned that something other than the AC weight on mine is preventing me from attaining better numbers?
The gas DA40's are typically lighter, and they have 10-12 more horsepower, at least when new. I don't have the AFM, but I would expect them to climb a little faster to about 8,000'.

The climb performance tables are based on weight because that is a big factor on climb performance. While the alternator draws a little power away from the engine, I don't think it's enough to materially affect the ROC. Having AC will just increase the weight by 88lbs.

I raise my flaps at 300'AGL, then climb at 88KIAS and 92%. My expectation is to average 600-700fpm.

On a recent flight I departed and climbed to 9,500' MSL from 120'MSL. I was solo with full tanks which came to 2,494 TO weight. Interpolating the AFM, the expected ROC would be 780fpm. From Flysto, the climb took 13min which works out to an ROC of 730fpm. But during that climb, my VS ranged from 425 - 1,014. The widest variation was in the first 3,000'. But from 3,000' - 9,500' there were still significant swings.

Departing Santa Fe one morning my ROC swung from 1,200 to -47. Power at 92%, pitched to 88KIAS, and descending at -47fpm! Fortunately I was about 5,000' AGL when that happened. Climbing out of Tucson last May I saw it swing between 100 - 1300. I routinely see big updrafts lasting 5-20sec departing my home airport. DA, updrafts, downdrafts and mountain waves have a dramatic effect on climb performance.

I have no doubt that somebody saw 1,200fpm, but I'd be very skeptical that they sustained 1,200fpm for an 8,000' climb. I think you can expect to get climb performance pretty close to the AFM. However, my typical cruise (85%) yields about 4-5KTAS better than the AFM.

The best way to measure your performance is to upload the Garmin logs to Flysto. Compare what actually happened to the AFM.
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