Glide ratio DA42-VI

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foup2k12a

Glide ratio DA42-VI

Postby foup2k12a » Tue Feb 14, 2017 5:47 am

What is the glide ratio both engines out and feathered? I could not find the info in the POH I could find on the web, it cannot be possible that this is not documented somewhere (unless manufacturer guarantees dual engine failure can never happen :) Thanks.
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CFIDave
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Re: Glide ratio DA42-VI

Postby CFIDave » Tue Feb 14, 2017 4:17 pm

I don't believe that certification testing is required to determine glide with both engines shut down and feathered for twin-engined aircraft -- so there is no glide ratio or "best glide speed" akin to that of a single-engine aircraft. Instead, considerable certification testing is used to evaluate single-engine performance.

Dual engine failure (which could potentially be caused by bad fuel) is extremely rare. Sadly, fuel exhaustion in twins is less rare.
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Re: Glide ratio DA42-VI

Postby Colin » Tue Feb 14, 2017 10:47 pm

Pretty sure Dave is offering to test it for us. You can start at 7,500.
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Re: Glide ratio DA42-VI

Postby Antoine » Tue Feb 14, 2017 11:09 pm

Wooooot? I did take a look at the AFM and could not find the information. Fuel starvation / bad fuel is a very real risk and I am shocked that the data is not published...
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Re: Glide ratio DA42-VI

Postby Colin » Tue Feb 14, 2017 11:20 pm

Reminds me that when the Gimli Glider pilots realized they had lost both engines they also found out that there was no checklist for "lost both engines."
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Re: Glide ratio DA42-VI

Postby CFIDave » Wed Feb 15, 2017 12:07 am

To Diamond's credit, the first "Emergency Procedures" item listed in Diamond Flight Training's published DA42NG/-VI checklist is ENGINES OUT LANDING, which does list a minimum 84 KIAS approach speed (the standard Vref approach airspeed for flaps APP or LDG). But this isn't necessarily the same as "best glide" speed to go the furthest distance to reach an airport runway:

1 Mayday call .................................... CONSIDER 1
2 Engine masters (2) ................................... OFF 2
3 Alternators (2) ......................................... OFF 3
4 Fuel pumps (2) ........................................ OFF 4
5 Fuel selectors (2) ..................................... OFF 5
6 Avionic master ......................................... OFF 6
7 Safety harnesses............. FASTENED and TIGHT 7
When sure of making landing area:
8 Flaps .......................... APP or LDG, as required 8
9 Approach speed .......................... min 84 KIAS 9
10 Power levers (2)...................................... IDLE 10
Gear UP landing After touchdown:
11 Electric master ......................................... OFF 11
Gear DOWN landing
11 Gear ..................... DOWN, 3 GREENS CHECKED 11
12 Electric master ......................................... OFF 12
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Re: Glide ratio DA42-VI

Postby foup2k12a » Wed Feb 15, 2017 3:58 am

Really surprising that there is no best L/D chart, borderline unacceptable from Diamond. SETP like Piper Meridian do have a chart (about 18:1) and some could argue that turboprop failures are less frequent than dual engine failures (piston).
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Re: Glide ratio DA42-VI

Postby CFIDave » Wed Feb 15, 2017 12:49 pm

As you noted, the Piper Meridian -- as a single engine plane -- must include best glide info. Multi-engine aircraft (not just those from Diamond) do not.

The only dual engine failure in a DA42 of which I'm aware happened years ago when a pilot took off with a dead battery (the plane was "jump started"). When the gear was raised, the resulting voltage drop from the weak battery caused all Thielert engine ECUs to go offline, and the engines to stop. The pilot landed in a field.

As a result, Diamond modified the DA42 design (for Austro as well as Thielert-powered aircraft) to include four 12-volt Panasonic backup batteries to power just the engine ECUs. The DA42 can lose both alternators and its main ship's battery and the engines will continue to operate normally.
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foup2k12a

Re: Glide ratio DA42-VI

Postby foup2k12a » Thu Feb 16, 2017 4:03 am

Thanks. Do you guys have an idea of the glide ration both engine feathered , 5:1, 10:1, 15:1? Thx

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