Miles M.35 & M.39 Libellula

[Mossie]

The Miles M.35 & M.39B Libellula (named after a Dragonfly) have been two of the most intriguing aircraft to me since I got into aviation at an early age.  Their canard/tandem wing layout has always struck me as well outside normal conventions & I've always wondered how they would have faired had they been developed & gone into production.

The M.35 was a proof of concept aircraft, designed & built in only six weeks.  It's basic design was intended as a naval fighter, it had a pusher prop & low wing with a high canard/second wing. I've always wondered what the definitive design might have looked like, the M.35 had only a wimpy DH Gypsy Major engine & would have needed considerable development to turn it into a fighter.



Miles moved on pretty quickly to a bomber design.  The Miles M.39 was to be powered by three jets & intended, although twin Merlins would probably have powered it until the jets were ready.  It was the reverse configuration to the M.35, a high main wing & low canard.  The M.39B was built as 5/9th scale demonstrator.  The design seemed promising, but interest fizzled out.



I've never quite been able to determine exactly why the Libellula designs were never developed further.  Part of seemed to be lack of official interest in an unproven design.  Miles had a reputation as a Maverick too, constantly getting into trouble with the authorities because they did things their own way, this might have had a bearing on why miles only really got to build training & liason aircraft.



A nice build article on IPMS Stockholm on various British canard & tailless aircraft:
http://www.ipmsstockholm.org/magazine/2006/06/stuff_eng_hrubisko_tailless.htm

Simon.

[kitnut617]

I might be able to shed some light on the subject Simon, Air-Britain has just released a new book called The Miles File.  But there have been a number of small articles in the quarterlies that Air-Britain have when you take out a membership with them.  Anyway, in the Spring 2009 issue of Air-Britain's Aviation World there just happens to be a page on the Libellulas.

First off though they aren't canard aircraft, because both wings were designed to create lift whereas a true canard wing doesn't, and it's just called a forward wing.  The design was geared towards a carrier aircraft where superior forward vision and slow landing speeds were essential along with good performance once airbourne (it was supposed to be a fighter).  The first one was built in great secret in 1941, even to the Air Ministry, and as you probably know all aircraft companies were under strict orders at that time to build just a few aircraft types that the Air Ministry deemed essential to the war effort.  When it was finally revealed to the Air Ministry, they were to put it bluntly, pissed off and Miles got into a lot of poo-poo because of it.  You might think that Miles would have got the message but believe it or not, the second one was also built in great secrecy too, the Air Ministry not knowing about this one either.  So I think that Miles so ticked off some 'higher-ups' that he was practically 'blackballed' in the Air Ministry.

But to answer your question about the ultimate design you only have to look at the cover of BSP, Fighters & Bombers 1935-1950 to see what might have come about.  The Vickers Type C bomber isn't a canard either but a true Libellula.

Robert

[Mossie]

Unfortunately I can't find that book Robert, the only Air Britain title I can find is Miles Aircraft: The Early Years 1925-139.  It might be a bit too new, I'll my eyes open.

Sorry, I realised it was a tandem wing aircraft, I just used canard because that's often how you see it put, a bit lazy of me.  I particularly like tandem wing aircraft, I often wonder why they haven't been used more, especially in low speed roles.

I was thinking more in the terms of how Miles aircraft might have developed, although the Vickers C would have been the ultimate tandem wing aircraft.  Beauty & the beast!

[jcf]

The 1942 Fleet Fighter proposal, for which the M.35 was a sub-scale proof-of-concept, was to be powered by a R-R Griffon.
The M.35 was designed by Ray Bournon under the supervision of George Miles.

Thread on Secret Projects:
http://www.secretprojects.co.uk/forum/index.php/topic,3585.0.html

Aeroplane Spotter page in PDF:
http://museumofberkshireaviation.googlepages.com/tandem_monoplane.pdf

Air Enthusiast Five has a Pilot's Notes article by Eric Brown about flying the M.39B, he relates that
the flight characteristics were '"interesting". 

The Putnam volume Miles Aircraft since 1925 by Don L. Brown (with Miles from the earliest days)
covers the various permutations of the Libellula (text, model photos, drawings), including an early Heavy Bomber
concept and the M.39 High-Speed bomber projects. Evidently these two originated with Don Brown.

I've attached scans of the early six-Centaurus powered Heavy Bomber concept (Brown)and the later eight engined
beast (Miles & Bournon), it was to be powered by either 2,300 hp R-R P.I. 26( Griffon sub-type or Eagle?) or 2,500hp
Napier Sabre.

Jon

[kitnut617]

Unfortunately I can't find that book Robert, the only Air Britain title I can find is Miles Aircraft: The Early Years 1925-139.  It might be a bit too new, I'll my eyes open.

Oops, my mistake, that's the one Simon.  

Anyway in the article it says that the very first flight nearly ended in disaster, first the thing wouldn't take off, and then once George Miles did get it off the ground (by chance apparently) he found it was very dangerous in pitch and only managed to get it down with a bit of luck.  After moving some ballast around it flew a bit better, but this led to the discovery that these type of aircraft had a very wide cg differential, they just had it in the wrong place on this first flight.  The front wing was designed to take about 30% of the lifting.

[jcf]

With the supersonic designs, the yanks had cart-blanche access to all of Miles' work & he was ordered by the Air Min. to give them everything & to hide nothing. Then the Brit Govt. whimped-out & decided that high-speed aircraft testing was too dangerous for humans to try --

The X-1 was certainly NOT a copy of the Miles M.52 but the way I read it (book on the Sound Barrier) was that the tailplane of the X-1 was the problem (buffeting or incidence). Bell persisted with a standard tailplane with elevators & it was only after they replaced it with an all-moving tailplane that they broke the Barrier -- Miles had an all-moving tailplane on his design from the beginning !!

But aren't we getting off-topic ?

The much ballyhooed information transfer came after the cancellation of the M.52 and thus after the XS-1 had already been
designed, built and flown.

The Bell design had an adjustable incidence tailplane from the beginning, indeed it was a feature that the NACA insisted on.
The Bell tailplane design and the one-piece 'slab' tailplane of the Miles design are two different animals. On the Bell design the
elevators functioned normally at low speeds, at transonic/supersonic speeds the elevators were locked and and all control
movement was accomplished by the stabilizer incidence control jack, in practical terms the stabilizer and locked elevators functioned
as a slab tail at high speeds, but it was a different concept and not based on Miles work, also the one-piece all moving horizontal
tail wasn't original to Miles either as it had been fairly common in the early days of flight. The so often mentioned 'big change' to the
X-1 tail made prior to the supersonic flights was to increase the power and speed of the stabilizer control jack, not the installation of
an all-moving tail. Anyhow the US had begun their own 'high-performance' all-moving tail work in 1943.  The XP-42 was modified to
have an all-moving tail and the program continued through 1945.
The 1946 NACA report on the XP-42 tailplane tests:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930081790_1993081790.pdf

A wartime report: Preliminary flight research on an all-movable horizontal tail as a longitudinal control for flight at high Mach numbers
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930092870_1993092870.pdf

As to Eric Brown's comments on the M.39B, he enjoyed it more for its oddity value rather than its flying characteristics.
Stall performance was good, indeed if no flap was applied it couldn't be stalled. How it stalled was dependent on the forward
and rear flap settings, under certain conditions an "unpleasant" porpoising was the result. Engine-out performance was also
"unpleasant". Brown states that he was unconvinced as to the potential benefit of the layout for as a ship-board fighter however
he also felt that the concept had potential as a high-speed bomber, which was the intended role of Brown's M.39.  Miles inspiration
for the Libellula design was the Westland-Dellane P.12.

George Miles was an interesting fellow but he had some blind-spots, one of which was his staying married to low-aspect ratio,
thick section wings, which worked fine for sport-touring aircraft but were poorly suited for high-performance fighters and
the like. Don L. Brown speaks of going round-and-round with George over the issue.

[pyro-manic]

The M.39 has me intrigued - wouldn't the low-mounted front wing cause some rather nasty problems at certain angles of attack, when it masks the rear wing?

Interesting designs, I must say.

[Mossie]

I guess that's the reason for the M.35's high forward wing, in a fighter high angles of attack are likely.  In the M.39, because it was multiple engined, it was easier to mount them from a high wing.  It's bomber role would have made high angles of attack less likely.  With the props washing over the wing it should reduce the risk of stall, although the jet version might have been a bit more touchy?

[jcf]

Don Brown reversed the wing levels between the M.35 and the M.39 to keep the aft wing out of the downwash of the forward wing.
Something to remember is that aircraft of the period did not operate at modern angles of attack, basically they couldn't, so the issue
was not as critical. The jet Libellula was to be a high-speed mailplane so high AOA maneuvering wouldn't have been an issue.