DH Hornet and counter rotating props

tigercat2 · February 26, 2015, 07:03:47 AM

I just finished an old Frog DH Hornet, and in doing some research on it, I found that it had counter rotating propellers. According to Eric Brown, this was his favorite piston engine aircraft, due in no small part to the amount of power and no torque due to the counter rotating props.

In his book and in other places I have read about the terrible takeoff tendencies of the Mosquito; it did not have counter rotating props and could be a real handful. This begs the question; Why did the RAF not insist on counter rotating props on the Mossie; it could not have cost that much, and would have saved many aircraft from being written off.

For that matter, why not counter rotating props on most twin engine aircraft, such as the F7F, A-20, etc. Sure you have to have a reduction gear to allow for the rotation on one prop, and a "handed" prop, but this was no problem for the thousands of P-38s that were built.

Wes W.

Go4fun · February 26, 2015, 08:00:17 AM

Probably something to do with Military Intelligence. The two words counteract each other! Or it might have been "Penny wise, pound foolish" at work. They wanted to save money on the counter-prop equipment and wrote off some aircraft for their efforts.

pyro-manic · February 26, 2015, 08:20:01 AM

The extra design work and time lost while implementing the changes on the production line, the extra parts and spares required, the differing maintenance and procedures required for the two separate types of prop/gearbox/engine etc. They are fairly minor alone, but they all add up to quite major practical and cost obstacles, particularly in wartime when you want things to run as smoothly as possible with no disruption.

tigercat2 · February 26, 2015, 08:55:22 AM

Good answer. If I had been King of aircraft production, I would have decreed that ALL twin engine aircraft, military and civilian, have counter rotating props. From the accident and incident reports I have read, this one act would have saved many aircraft.

After all, this concept was good enough for the Wright Brothers, so it should have been used from the beginning.

Wes W.

PR19_Kit · February 26, 2015, 01:50:09 PM

At least they avoided the problems that the Twin Mustang had. When it was first built it wouldn't fly until they reversed the rotation of BOTH engines, then it was OK.

What they actually did was swap the engines and props from one fuselage to the other of course.

tigercat2 · February 27, 2015, 07:22:49 AM

I recall reading about that issue on the twin mustang. Seems like the original rotation (can't remember whether they were inwardly or outwardly rotating) was blanking out the elevator or something similar and the aircraft, even though it had plenty of power, could not leave the runway. After the engines and props were switched, it became a very fine flying machine, but a little unreal when doing a roll (especially for the pilot in the other cockpit).

Wes W.

NARSES2 · February 27, 2015, 07:27:12 AM

Apparently the Beaufighter was really bad during take off. Wanted to pull away to one side, caused loads of fatal accidents

tigercat2 · February 27, 2015, 08:47:33 AM

Quote from: NARSES2 on February 27, 2015, 07:27:12 AM
Apparently the Beaufighter was really bad during take off. Wanted to pull away to one side, caused loads of fatal accidents

And how much would it have cost to have counter rotating props from the beginning; saving many lives and aircraft?

Wes

Caveman · February 27, 2015, 01:14:36 PM

It wasn't about cost, it was about expediency and logistics. Which, given the background, were more important. There are many pros and cons to standardisation in general.

PR19_Kit · February 27, 2015, 01:29:00 PM

Quote from: tigercat2 on February 27, 2015, 07:22:49 AM
I recall reading about that issue on the twin mustang. Seems like the original rotation (can't remember whether they were inwardly or outwardly rotating) was blanking out the elevator or something similar and the aircraft, even though it had plenty of power, could not leave the runway. After the engines and props were switched, it became a very fine flying machine, but a little unreal when doing a roll (especially for the pilot in the other cockpit).

On the prototype XP-82 the props rotated so that the inner blades were going upwards on the centre-line of the aircraft. i.e. the engines were rotating OUTwards at the top. The airflow from the props apparently stalled the wing centre section and when the engines and props were swapped over it flew perfectly, engines rotating INwards at the top.

Captain Canada · February 27, 2015, 04:31:00 PM

Interesting stuff here guys ! These are things I've never really thought of....

kitnut617 · February 27, 2015, 05:56:57 PM

Actually guys, the Hornet prototype had two Merlin 130's, both props turned in the same direction (same as any Merlin BTW and like the Mossie). The original requirement was for future installation of contra-props, but in the end they settled on counter-rotating props. Originally, these props turn the same as the XP-82's did (the port engine being a Merlin 131), that is they turned outwards from the top. Then after quite a few test flights in this configuration trying to solve numerous problems, (one being severe buffeting of the tail-plane which no matter what they did, wasn't cured), they swapped the engines over. Most problems went away after this was done and all Hornets then had the props turning from the top towards the fuselage.

There is a lot of praise about how well the Hornet handle, but the book 'The Hornet File' reveals that single engine landings was the cause of most fatalities of pilots who attempted to do it. The Navy banned all single engine landings on carriers.

Incidentally, the XP-82, P-82B,C,D had Packard license built Merlin 130/131's (BTW, the P-51H had a Packard license built Merlin 130) the only difference apart from American nuts & bolts, was the Merlin 130/131 had down-draft carburetors, and the Packard equivalent had up-draft ones (like all previous Merlins)

maxmwill · February 28, 2015, 04:08:18 AM

I saw the title of this and thought that the Hornet had contrarotating props, not handed turning, but contrarotating props, that is,, two props per engine, but, after reading through the thread, realized my mistake.

But then, why not? Didn't the Shackleton have contraprops? And how successful was that?

Instead of the Merlin engines, what would have been the performance of the Hornet with Griffons and contraprop?

Might it have suffered the same fate as the Hughes XF-11?

Or, had it been accepted by the RAF, might it have found a career in high speed high altitude recon?

pyro-manic · February 28, 2015, 07:07:36 AM

The Hornet was specifically designed around the Merlin 130/131. Sticking Griffons (bigger and heavier) on would have upset the balance of the entire design. And it didn't need Griffons because it was blazingly fast and powerful with the Merlins.

PR19_Kit · February 28, 2015, 07:42:49 AM

Quote from: kitnut617 on February 27, 2015, 05:56:57 PM
Originally, these props turn the same as the XP-82's did (the port engine being a Merlin 131), that is they turned outwards from the top. Then after quite a few test flights in this configuration trying to solve numerous problems, (one being severe buffeting of the tail-plane which no matter what they did, wasn't cured), they swapped the engines over. Most problems went away after this was done and all Hornets then had the props turning from the top towards the fuselage.

Interesting.

I wonder if the problems were for the same reason as the XP-82's, i.e. the inner wing sections stalling, but perhaps on only one side?