Prop speeds

[Boslandew]

Can someone tell me roughly the operating range for prop speeds on a turbo prop aircraft? My Google search gives me every detail known to man except prop speeds.

Much obliged

[Green Guard]

any... to just under speed of sound... :D

[Boslandew]

Sorry, I should have said rotational speeds

[tommoutrie]

well thats probably still true. Tip speeds get close to and sometimes through the speed of sound - boeing stearmans make the rasping noise they do because of the tips going supersonic. A 90" prop on something like a king air is describing a path about 7 metres round and at 2200 rpm thats ..um M0.78.
Saturday afternoon maths of course..

Do you mean just rpm? if so, no idea, google is your friend

http://www.enhanced.aero/pdf/performance_raisbeck.pdf

(might be talking rubbish.. am sitting here watching the F1)

[safelife]

Q400: 850 to 1020 rpm. The smaller ones up to 1200 rpm.

[Boslandew]

Gentlemen

Many thanks, just what I was looking for. Theres always an answer if you ask the right bloke.

Boslandew

[Tinstaafl]

Safelife, just clarifying something, but I presume you mean the smaller Dash 8s? And not smaller turboprops in general - because the Kingair I fly is around 2200 rpm, not 1200

[EW73]

Just to add another, larger diameter turbo-prop to the mix.

The Lockheed P3 Orion, and therefore the Electra props are constant speed (in flight) at 1,021 rpm, with an 11 foot diameter prop if I recall!

Though the Electra had square-tipped and the Orion round-tipped prop blades.

[Dufo]

L410: 2080 max (takeoff), 1900 climb, 1700 cruise
Saab340: 1380 max, 1230 climb and cruise

[Big Pistons Forever]

Homebuilts powered by Volkswagen engines typically have a 3300 RPM redline.

However if you wanted to generalize:

Large Turboprop airliners (30 plus seats): prop RPM range 800-1200
Small Turboprops.................................................. .....1700-2200
Pistons engines ........................................................1800-2700

[barit1]

The BIIIG pistons had even slower-turning props.

For example - P&W R-4360-4
Max crankshaft RPM = 2700
Reduction gear ratio = 0.425
Resulting prop RPM = 1148

Other R-4360s had gear ratios as low as 0.333, for prop rpm = 900.

[Tu.114]

DH8D:
maximum (takeoff/go around) 1020, as has been mentioned; climb power 900, cruise power 850 (also useable for climb and landing; brings some reduction in noise and performance).

DH8C: Maximum 1200, intermediate setting 1050, cruise 900 rpm. Also on this series, 900rpm is allowed for climb and landing with some performance penalty but noticeably less cabin noise.

NK-12 powered turboprops (Tupolev 95, An-22): 700rpm, which results in supersonic tip speeds due to the large propellers. Still seems to be efficient though.

[Clandestino]

IIRC (five years have passed) ATR 42-300 with PW120 and Hamilton 14SF5 four bladed props used 100% for takeoff and approach, 86% detent for climb and 77% for cruise when out of icing conditions, 100% being 1200 RPM. We could set RPM anywhere between detents and often used 92% for cruise in icing conditions as it was less noisy than 86%, increase in consumption was minuscule and cruise speed (250 KTAS) not affected.

[Boslandew]

Many thanks for the further info. As an ex-rotary man I had thought that cruise rpm would have been about 2000 as with piston engines, say DC3. An eye-opener to see rpm as low as 850.

Boslandew

[MarkerInbound]

Looked through a couple old manuals, both the P&W 1830-94 and Wright 1820-80 have 16/9 reduction gears. So if the engine is turning 2050 rpm in cruise, the prop is turning about 1150 rpm. I know R985s don't have a reduction gear and judging from the sound R1340s don't either.

[barit1]

There are both direct-drive and geared (3/2) versions; the direct-drive model is much more common. The geared version (R-1340-AN-2) was built primarily for large blimps, with oversize prop for low-speed efficiency.

[Boslandew]

The logical question has just occurred to me. Why should turboprop rpm be half that of a piston engine on a comparable type, say DC3 against DH8C.

Probably not a good comparison of types but I hope you get the point I'm trying to make

[aerobat77]

Why should turboprop rpm be half that of a piston engine on a comparable type, say DC3 against DH8C.

it is not. the dc3 has 16/9 reduction gearing so 2000 engine rpm are far not 2000 prop rpm.

i think the extreme was a lockheed starliner where the engine turned the props via a .355 gearing so prop speeds were something about 750-800rpm in cruise .

[Boslandew]

Aerobat

Probably didn't use precise enough terms. According the Pilots Notes Once had, the DC3 Prop turns at about 2000 RPM plus or minus a bit in the cruise, nearly twice that quoted below for, say, the Q400. Have I missed something?

[barit1]

No, the DC-3 CRANKSHAFT turns ~2000 rpm (that's what the cockpit tach shows).

The prop turns 56.25% of that speed, or 1125 rpm - because of the gearing ratio.

[Cardinal]

Emb-120 / PW118 1200RPM
B-1900 / PT6A 1700RPM.

[Boslandew]

Barit

Many thanks. As I said I am a rotary pilot and had always assumed the figure was prop speed. You live and learn.

Boslandew

[barit1]

You live and learn.

Yes, don't we all!

:ok: