Lancair Evolution- Turbo prop

[Ted]

Is that because of composite wings, fuel efficiency from no loss of bleed air, the battery capacity of the 787?

As I understood it, the design decision mostly had to do with the engine efficiency from no loss of bleed air. The battery capacity isn't it, and I don't think the composite wings are, either. The engines on the 787 have massive alternators on them. I forget the amount of power generation they provide, but the alternators are enormous and the power takeoff to run them is ridiculous. But, the theory is that it's more efficient than robbing bleed air, and there's probably a good amount of truth to that.

 

[bnt83]

As I understood it, the design decision mostly had to do with the engine efficiency from no loss of bleed air. The battery capacity isn't it, and I don't think the composite wings are, either. The engines on the 787 have massive alternators on them. I forget the amount of power generation they provide, but the alternators are enormous and the power takeoff to run them is ridiculous. But, the theory is that it's more efficient than robbing bleed air, and there's probably a good amount of truth to that.

Every time I imagine it I think of some mad looking oil/water/fuel cooled 1000+ amp thingy. As for efficiency gains, I can't say for sure but seems like it wouldn't be that much to me.

 

[KA550]

Just the 500 and 550. All the CJs, the 560, and 560XL are bleed.

EDIT: Now that I think about it, I'm not sure about the earlier 560s - I just flew the Encore. Could be electric on those.

The straight 560 (Citation V) inboard sections are bleed air.

 

[kayoh190]

The straight 560 (Citation V) inboard sections are bleed air.

Ah - thanks. That rings a bell from way back when I did V differences from II training - I seem to remember the generators being beefier on the II to support the electric inboard portion. I can't begin to imagine how much juice it takes to heat the wings on a 787. Pretty mind boggling!

 

[Ted]

Every time I imagine it I think of some mad looking oil/water/fuel cooled 1000+ amp thingy. As for efficiency gains, I can't say for sure but seems like it wouldn't be that much to me.

I think it's got two alternators per engine. I forget the amps, but the voltage is pretty high, too. Total power production is rather insane.

You might be surprised at the efficiency gains. If nothing else, it allows the engine to be optimized and not have to worry about bleed air, which impacts things like compressor stalls, EGT margins, etc. That can allow you to run a bit tighter. I'm not saying that's what's done, just that it's possible. Also, Boeing was going after lots of little efficiency gains to get the plane to be as efficient as it is.

 

[Luvrv8]

I watched this one happen.

http://www.ntsb.gov/aviationquery/brief.aspx?ev_id=20080903X01363&key=1

 

[MachFly]

Well, keep in mind my basis for comparison is piston twins, which don't have very good visibility, either.

Understood. Since twins don't have terribly bad visibility either, it sounds to me that Lanceair's visibility shouldn't be an issue.