DA40 XLT Performance vs. XL/XLS

Any DA40 related topics

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dmloftus
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Re: DA40 XLT Performance vs. XL/XLS

Post by dmloftus »

CFIDave wrote: Sat Apr 03, 2021 9:23 pm The one thing that CAN affect performance very slightly is the propeller, since there may be 3 different props found on these aircraft:
- Wood-core (with composite covering) 3-blade MT
- Aluminum 2-blade Hartzell
- Composite black Hartzell with 2 scimitar (wider) blades

See attachment describing DA40 prop options (published back in 2008):
Hi Dave,
Maybe a dumb question. The document attached indicates the MT prop can run "2700RPM max continuous". The AFM checklists all indicate a max of 2400RPM "above safe altitude". And the power charts only go to 2400RPM. I always back down to 2400RPM >500'AGL on takeoff, then cruise 2200-2400. Section 2.4 limits max continuous RPM to 2400 and 7.9.1 limits max continuous power to 2400RPM at sea level and ISA. Can you actually run at 2700RPM (or anything above 2400?) continuously above some altitude? How much additional speed could be gained cruising at 2700RPM vs 2400? I always guessed that the limiting factor was the IO-360, not the prop. Does anyone exceed 2400RPM for any period of time other than take off?
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MarkA
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Re: DA40 XLT Performance vs. XL/XLS

Post by MarkA »

There's an Airplane Flight Manual Supplement that changes the operating limitations to allow 2700 continuous RPM for the MT prop (see the attached).
Attachments
2700 RPM supplement.pdf
(1.61 MiB) Downloaded 102 times
2010 DA40 XLS, N123MZ, KHIO
https://youtu.be/LuQr6mGxffg
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Re: DA40 XLT Performance vs. XL/XLS

Post by dmloftus »

MarkA wrote: Mon Apr 05, 2021 8:00 pm There's an Airplane Flight Manual Supplement that changes the operating limitations to allow 2700 continuous RPM for the MT prop (see the attached).
Hi Mark,
That's very interesting, I never caught this. Still 7.9.1 is not changed limiting 2400 max continuous at sea level and ISA. So how high do you need to be to run continuously above 2400? And how much speed benefit can you gain?
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Re: DA40 XLT Performance vs. XL/XLS

Post by CFIDave »

My understanding is that the 2400 RPM limit was originally provided to meet European noise regulations.

To get the full 180 hp (at sea level) or maximum power, you need to operate at 2700 RPM (It'll be noisy and won't be very fuel efficient). 2400 RPM provides a good compromise between power and efficiency, so I usually instruct pilots to pull the RPM back to 2400 shortly after takeoff. The Powerflow exhaust is "tuned" to 2450 RPM, which is pretty close to that value.

One situation where greater than 2400 RPM may be warranted in cruise is when flying above 8000 feet. If you think of the engine as a big air pump, additional RPM will cause a greater flow of fuel-air mixture through the engine. This will counter low manifold pressures at high altitudes, where a major drop in power output occurs. So when flying above 8000 feet I may choose to increase cruise RPM to 2500 or even 2600.
Epic Aircraft E1000 GX
Former DA40XLS, DA42-VI, and DA62 owner
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