Propellors on DC6/7, Stratocruiser, Constellation & Britannia

[b377]

( This thread also appears under TechLog my appollogies for repetition I'm not sure which heading is best)

On topics about the DC6, DC7 and Constellations & Stratocruisers mention is often made of the props used on the Wright and P&W engines as being either Curtiss Electric (CE) or Hamilton Standard (HS).

I have had a long standing query as to why some aircraft like the B377 used square tipped props on some a/c while other Strats (even owned by same operator such as BOAC) used rounded tips? Same goes for the DC6 and DC7s. Is it possible to visually tell apart a CE vs. HS propellor?

I have also noticed on a few Britannia pics that some a/c have rounded tip props and others square tipped and even seen mixed square/round props on same a/c. These were presumably Rotol?

I know prop hub spinners were optional kit so this easily explains this difference.

[WHBM]

I believe the BOAC Strats that had the different type of props were secondhand acquisitions. There were window differences on the airframe as well.

[b377]

Strat Windows

Yes, Pan Am, BOAC, North West, United & SAS all ordered their own window shape preferences for the main and lower cabins (bar) not sure if ordering different tipped props served a similar cosmetic purpose

(BOAC did of course acquire ex Pan Am & United airplanes and all of the SAS fleet from new.)

[evansb]

Generally, tapered blades are capable of higher speeds, and squared-off blades push more air for a given RPM and air density. Chord, aspect ratio, sweep, pitch and tip speed (mach) are all major factors when matching a prop to a specific engine application.

Note that most Vickers Viscount 700-series have tapered tips and Viscount 800 series have squared-off tips. The photo below shows an early BEA 700-series Viscount with experimental high-speed tips. Efficiency and noise are major considerations in propellor design, not aesthetics.

[b377]

All very well but that still leaves the fact that both tappered and squared-off tips were used interchangably and at times the same airframe sported the two types at the same time. There is a very good pic in airlines.net showing a Britannia fitted with mixed tip props.

To me squared tip props are 'smarter' looking.

[evansb]

The photos on airliners.net of Britannias with dissimilar propellors are both Canadian Pacific Airlines Britannias. Both aircraft have the dissimilar prop installed on the number two engine. One photo shows a near-new aircraft outside the company hangar in Vancouver. The tapered tip propellor has rubber boot leading edges versus the bare edge of the square tip propellor. Given the intake icing problems of the Bristol Proteus engine, perhaps this unusual propellor configuration was an in-service test and assessment of props and icing.

Whatever the reason, it is thought provoking.

A good example of propellor suitability is the Lockheed L-188 Electra/P-3 Orion. Both models are powered by the Allison turboprop, but the operating profiles of the two models are quite different. Wth the exception of the original American Flyers and KLM Electras, the Electra has square-tipped props, and the P-3 has round-tip props.

[b377]

Photos: Bristol 175 Britannia 312 Aircraft Pictures | Airliners.net

this link shows the pic in question, an in-service BOAC 312 with mixed props (at least on 3 & 4).

One example of many I've seen not just on the Brit but also b377 & dc6/7.

Obiously something to do with spares holdings and interchangability.

[b377]

Mixed Job

Bingo!

[WHBM]

Originally Posted by evansb

The photos on airliners.net of Britannias with dissimilar propellors are both Canadian Pacific Airlines Britannias. Both aircraft have the dissimilar prop installed on the number two engine. One photo shows a near-new aircraft outside the company hangar in Vancouver. The tapered tip propellor has rubber boot leading edges versus the bare edge of the square tip propellor. Given the intake icing problems of the RR Proteus engine, perhaps this unusual propellor configuration was an in-service test and assessment of props and icing.

Whatever the reason, it is thought provoking.

Could the photo have been taken when they were 1/4 way through a prop change ? Would have thought an unbalanced mixture would be bad news (rather like mixing your tyre types on the ar).

[b377]

Round tips

Round

[b377]

Squar tip

[b377]

Que lastima pobre avion !

[b377]

Smart square props !

[evansb]

In the Britannia examples, the tapered tip, rubber-booted props were located on the inboard engines. As well, the Britannia photos were taken in the early days of the Britannia's career. I don't see any examples of dissimilar props in later photos. Any ex-Britannia engineers care to comment?

[Brian Abraham]

Taken from the respective type certificates. Well you did ask.

Britannia 305
De Havilland P.D. 202/4N6/2
De Havilland P.D. 208/466/2

DC-6
Hamilton Standard
43 D60/6825 (Not permitted on -83A or -83AM3 engines)
43D60/6841
43D60/6851
43D60/6873
43E60/6895 (Only prop permitted on CB16 engine. Only prop permitted on DC-6A and –6B)
Curtiss
C632S-B/744-6C2
C632S-B/744-4C2-0
C632S-B/744-10C2
C632S-B/836-14C2
C642S-B/836-14C2-18

DC-7
Hamilton Standard
34E60/6921
34E60/7019 (DC-7C only)

Boeing 377
Hamilton Standard
Hub 24260 fitted with either 2J17B3-8W, 2J17F3-8W or 2J17H3-8W blades
34E60/7015-29 (Supplemental Type Certificate for use on 377MG [Cargo only aircraft])
Curtiss
Hub C6445-B302, Blades 1052-2004-30

Constellation 1049
Hamilton Standard
43E60/6901-02
43E60/6903B-0
43H60/6959B-0
43H60/6967-0
Curtiss
Hub C634S-S, blades 858-5C4-0
Hub C634S-C500, blades 830-21C4-0
Hub C634D-A2, Blades 109652-12
Hub C634D-A4, Blades 109652-12

Anorak off.

[pjac]

Pardon me for saying, EVANSB- but the Proteus engine was a Bristol, not a Rolla

[Brian Abraham]

True pjac. Stanley Hooker (later Sir) was head of the program if I recall. He later lead RR and came out of retirement to get the problems on the 211 solved. Did RR take over support of the engine after Bristol sank out of sight? Maybe source of EVANSB comment.

[b377]

Prop manufacture list

evansb ...Quote: " were taken in the early days of the Britannia's career. I don't see any examples of dissimilar props in later photos .... "

The picture of the BOAC Britannia above featuring mixed props is from May 1958, I wouldn't call that early in its carreer - if the 102 is included of course.

Brian Abraham

Thanks for the Brit prop info I thought they were made by Rotol as in the Hovercraft that also use the Proteus engine much later.

As regards to the B377 prop list, several blade options were apparently available for a given hub, some may have been tapered others square (?) explaining the difference but otherwise interchangable.

However a wing symetric arrangement must have been necessary to avoid differential torque problems (unless both blade types were equally effective at a given pitch and RPM )- In the case of the Britannia the 4 Proteus engines were intended to run synchronised to reduce vibration, although this was never achieved exactly I was told once, which explains the characteristic slow modulation (beat) in the sound of a Brit flying in the distance as the engines came in and out of phase.

Oh that Wispering Giant !

[evansb]

Yes pjac is correct. Bristol built the Proteus.

The Bristol Siddeley Proteus was quite an engine, powering the Saunders-Roe Princess flying boat, RN patrol boats, a frigate, a hover-craft, and even Donald Campbell's Bluebird land speed record car.

The Britannia entered airline service in 1957, so I would say 1958 is still early in the aircraft's career.

[dusk2dawn]

What kind of R-2800 had D-spline?