Increasing Engine Power

[Vfrpilotpb]

One of my Nautical relatives has explained to me that if you put a bigger engine and prop into a boat(speed boat or big boat) you cannot exceed the speed that was designed for the said boat, something to do with the water that the profile of the hull shifts,

Would that hold the same for Helicopters, say you placed the Astazou(spell) and MGB plus rotor from the Gazelle into the R44 would you get increased lift and increased speed I know the weight and balance thingy will be also needed to be considered, but what I am trying to see is, can Helis be engined up and perform better?

Like I once put a 10 ltr Perkins V8 diesel into a lWB Land Rover, the steeing was heavyish the brakes were crap but boy did that thing go! :D


Vfr

[NickLappos]

Vfrpilotpb,

The speed limits on a hulled boat are due to the fact that the bow wave created by the hull tends to grow longer as the boat speeds up, and when the wave reaches the stern, it adds to the wave from the stern. If you try to go faster, the wave gets deeper, but the boat goes almost exactly the same speed. In fact, the engine power starts making bigger waves, but the boat goes no faster. This is called the "Hull Speed" and is determined mostly by the hull length (the longer the faster).

Helos have something similar, because the rotor doesn't like being pulled thru the air at speeds much faster than about 170 knots. You can put bigger engines on, and get more payload, more lift, but probably little more speed.

The power required curve at high speed is actually a product of all the drags of the helo, but it is generally true that at Vmax, increasing power by 10% might only add 5 knots or so at 165 knots.

[helicopter-redeye]

I believe (simplistically) that it is all in the blade. But there is more to it than that in terms of overall airframe drag.

Perhaps a RR Viper in addition to the O540 would give a faster turnout for the R44???

;)

The real advantage of the turbine in a 44 would be cost (for the Jet A1 -v- Avgas) and possibly weight althought the extra fuel burn of the Astazou would have to be factored in.

Net Net. Wait for an R55??