Best Glide

Any DA42 related topics.

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RDGUSLLC
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Best Glide

Post by RDGUSLLC »

Can anyone offer the "Best Glide" for the D42? I am new to the aircraft.
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ememic99
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Re: Best Glide

Post by ememic99 »

It should be 82 KIAS.
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RDGUSLLC
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Re: Best Glide

Post by RDGUSLLC »

I meant what is the glide ratio. For example in the Meridian 600 it is 2.5 to 1 (2.5 miles for each 1000 ft of altitude). For the Cessna 206 it is about 1.87 for each 1000 feet. For the TBM it was about 2.25 to 1. Of course it is dependent on weight and wind but with a normal load and no winds, it is a helpful number.
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ememic99
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Re: Best Glide

Post by ememic99 »

This has been discussed here already - there’s no official data because it’s not required for twin certification.
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RDGUSLLC
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Re: Best Glide

Post by RDGUSLLC »

Thank you. I am new to the group. I had not read that.
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GearUp
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Re: Best Glide

Post by GearUp »

I wad told at the factory it is 9 to 1, even though it is not required being a twin.
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photoSteveZ
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Re: Best Glide

Post by photoSteveZ »

RDGUSLLC wrote: Tue Mar 15, 2022 2:44 am I meant what is the glide ratio. For example in the Meridian 600 it is 2.5 to 1 (2.5 miles for each 1000 ft of altitude). For the Cessna 206 it is about 1.87 for each 1000 feet. For the TBM it was about 2.25 to 1. Of course it is dependent on weight and wind but with a normal load and no winds, it is a helpful number.
To be slightly pedantic, "2.5 miles for each 1000 ft of altitude" is NOT a glide ratio of 2.5 to 1: you're dividing apples by oranges. Your Meridian's glide ratio is more accurately described as about 13:1 (13 miles for each mile of altitude).

Glider pilots use the term L/D ("lift over drag") to talk about glide ratio. A typical modern glider has an L/D of 40:1 or better; An A-36 Bonanza is about 10:1...but only if you remember to pull the prop control to coarse pitch when the engine quits. Dividing L/D gives the same value as glide ratio.

Glider pilots also know that the best L/D speed varies with weight (and with wind, as you correctly point out), but that the best glide ratio does not vary with weight: at higher weights the best glide speed is higher (and the best speed to fly into a headwind is higher as well), but the best glide ratio doesn't change.

I don't know what the best glide ratio of my DA62 is, but I know that at max gross weight it occurs around Vy, with the props feathered.
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Re: Best Glide

Post by mfdutra »

Gear up and both props feathered, the glide ratio should be much better than 9:1.

The problem is the gear. My understanding is that if you lost both engines, the gear would not be locked in the up position and will start hanging, generating a lot of drag. Can someone confirm that?
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Re: Best Glide

Post by Chris »

I think you'd run out of altitude before the gear would auto-extend due to loss of hydraulic pressure. The electric pump only runs periodically when the pressure drops below some threshold. You hear it pressurizing when you flip the master switch to on, so it can run off of just the battery.
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