The Baynes Carrier Wing Glider (or the Bat)
Mike Maufe has sent us the flight test report by Robert Kronfeld on this strange glider which is too long to repeat in full but part of it is given below, followed by an excerpt from "Testing for Combat" by Capt Eric Brown (published by Airlife Publishing Ltd who have given us permission to copy) (Chris Wills and I have added the rest Ed.)
But first we start with a small 3-view drawing from Norman Ellison's book, "British Gliders and Sailplanes 1922-1970 and a description of the glider from Aeroplane Monthly.
"NOTHING VENTURED" by Philip Jarratt. (Aeroplane Monthly May 1990)
In 1941 the British Sailplane Designer L.E.Baynes made a proposal that armoured fighting vehicles, such as the 8 1/2 ton tank, could be provided with detachable glider wings to enable them to be flown to battlefields behind tugs. At the time, Baynes was the aviation adviser to the Alan Muntz Company at Heston, which specialized in weapons, and he had organized a separate aircraft division of the company.
The military advantages of such mobility for airborne operations were self evident, and General Aircraft had considered the idea when developing the Hamilcar. In the Baynes proposal, however, the tank itself replaced the fuselage and undercarriage, and there was no tail, so that there was a great saving on weight. The glider would be cast off to make a free descent to the landing site, the tank's engine being started while it was still airborne. The wing would be detached on touch down using a quick release device and then would be carried away by its residual lift, allowing the tank to go straight into action. While Air Staff approved
of the idea in principle, they decided that it would be wise to explore its aerodynamic and control characteristics by testing a 1/3 rd scale piloted flying model.
This machine, known as the "Bat", was designed by Baynes and built by Slingsby Sailplanes at Kirbymoorside, Yorkshire in 1943. Built of wood throughout, it was aero-dynamically similar to the full size "Carrier Wing", but had a small nacelle, to accommodate its pilot. Its swept back wing had a single main spar. Although it had no airbrakes, it was fitted with Slingsby Patent bellows operated flaps, which extended outwards for about half the wing span on each side. These were located well in from the wing trailing edge to minimise change of trim and enable the full flap increment to be realized within the scope of the available elevon control. The elevons had tabs and mass balances, and the wingtip fins had deep-chord, mass-balanced rudders.
In the neutral position, the wingtip vertical surfaces were set at a small outwardly-inclined incidence. The nacelle tapered off to provide additional fin area. A simple underbelly skid formed the main undercarriage, a pair of small wheels being used for ground handling and take off. When at rest, the "Bat" settled on one of the wing tip skids built into the fins. The glider spanned 33 ft.
Control was by wheel and shaft through the main spar, operating a small rocking control box unit. Pushrods linked this unit with the elevon controls. Fore and aft and rotational movement of the control wheel gave equal and differential movement, respectively, to the elevons. The rudders had normal pedal control which gave differential in favour of the outward positioned rudder. Allotted the military serial RA809, the "Bat" was given green and dark earth upper surfaces with training yellow outer portions, and yellow undersides with black diagonal bands. As there was no fuselage to speak of, the serial number was applied to either side of the nose of the nacelle, and the roundel and the yellow encircled "P" which denoted a prototype were painted on the rear of the nacelle, behind the canopy. Flashes were applied to both sides of each fin, and roundels were painted on top of and beneath the wings.
A Famous Pilot.
The "Bat" made its first flight in July 1943, at the Airborne Forces' Experimental Establishment at Sherburn in Elmet, Yorkshire. Most of the test flights were made by Flt. Lt. Robert Kronfeld. Wind Tunnel tests at the Royal Aircraft Establishment (RAE) had indicated the possibility of wingtip stalling. So provision had been made for wingtip slots to be fitted. Because these were not ready in time, the aircraft was flown without them. Kronfeld found that there was no tendency for premature tip stalling. As the glider stalled normally the slots were never fitted.
Flight tests had shown the tailless glider to be practical, but the full-size carrier wing was not proceeded with because a suitable tank was not then available. Moreover, the decision had already been made to develop gliders which could carry tanks and other equipment within their capacious fuselages. However, as the "Bat" was the first modern tailless flapped monoplane to become available for full-scale research, it was fitted with a variety of recording instruments and flown extensively by the RAE to obtain data on the stability and control of tailless aircraft.
The "Bat" was last seen in 1958, dumped behind a hangar at Croydon.
| Baynes "Bat" data. |
| Wingspan:- 33ft 4 inches. |
| Length:- 11 ft 4 inches. |
| Wing area:-160 sq.ft. |
| Aspect ratio:-7:1. |
| Empty weight :-763 lbs. |
| Gross weight:- 963 lbs. |
| Wing Loading:- 6 lbs/sq.ft. |
| Max.Speed:- 120 mph. |
| Cruising Speed:- 80 mph. |
| Stalling Speed:- 40 mph. |
(The Vintage Centre at Lasham holds some of the "Bat's"
drawing plans.
They indicate that the "Bat" was heavily built, not as a performance sailplane, but to try out the idea. We have every confidence in L.E.Baynes as the designer of our Scud sailplanes and feel that he did not go far wrong with the "Bat's" aerodynamics, except that both elevons appear to have been up for max.lift and this would cause more drag, which should not happen. The Horten motorgliders, which have recently been designed and built in Germany, also reveal this, and it is brought about by the large cockpit for the pilot in the centre of the span where the aerodynamic efficiency is supposed to be maximum according to Horten principles. However, we feel that the "Bat" would make a very good tailless sailplane, if it was more lightly built, with more span and with a profile to give it more lift, especially at the wing-span's centre around the cockpit. However, both elevons up at the stall would give more geometric washout and a guaranteed gentle stall and L.E.Baynes was not after maximum efficiency when he designed it. It is clear that Robert Kronfeld at that time was enthusiastic about flying wings and in 1945, he organized the importation of the Horten 4a LA-AC from Germany to the RAE at Farnborough. He was killed near Lasham flying the tailless GAL 56 flying wing, before he could own and fly the Ho 4a, which was sold to the American Hollis Button in 1950, after damage had been repaired, which it had sustained due to an unfortunate ground-loop at the RAE) C.W.
Preliminary tests on handling and stall characteristics of a one third scale Baynes Carrier Wing Glider. By F/Lt R. Kronfeld A.F.C.
The one third scale Baynes Carrier Wing Glider is a tail-less single seater with elevon control (combined ailerons and elevator) and end plate rudders on the wing tips.
In free flight and tow the controls are well balanced and very responsive although the rudder is less effective than the other controls. The control forces are very light. With due allowance for lightness and responsiveness the aircraft is easy to fly except in rough weather conditions in which it handles like other aircraft of equally light wing loading. Generally the glider handles similarly to light and responsive sports type gliders of orthodox design.
This glider is a one third scale flying model of the projected Baynes 100ft span Carrier Wing, the purpose of which is to carry an 8½ ton tank or armoured vehicle as a glider to be towed by a tug aircraft in the usual manner. The span is 33 ft, the wing area 160 sq ft and the gross weight fully loaded with ballast is 963 lbs. The wing loading is 6 lb/sq ft.
The part of the tank which projects down below the wing on the full sized aircraft is replaced by a small nacelle on the underside of the centre section which contains the pilot's seat. A single skid undercarriage is fitted and there is a normal quick release for towing. Part of the pilot's body is in the wing and his head projects into a transparent fairing on the top surface of the wing.
Projecting through the main spar into the cockpit thus formed is a control shaft and wheel, which by fore and aft and rotational movement controls the elevons for longitudinal and lateral control. Independent rudder control from the rudder pedals in the nose of the nacelle is provided.
The glider is fitted with bellows type flaps which are operated by air through ducts from a point in the leading edge of the centre section and from a point in the upper surface. The flaps are so positioned in relation to the chord of the wing to produce the minimum change in trim and to enable the full flap increment of lift to be realised within the scope of the elevon control available.
The elevon control system consists of a direct incidence control of the elevons by fore and aft movement of the control wheel and differential angular movement about any mean incidence setting produced by rotational movement of the control wheel, thus giving lateral control for any mean setting without change of fore and aft trim.
The rudder control consists of a normal rudder pedal arrangement
connected to the rudders to give a differential movement to the
rudders in favour of the outward turning rudder. In their neutral
position the rudders, together with the fins, are inclined slightly
outwards to the rear in order to provide a directional dihedral.
Handling in free flight
The control in free flight is very satisfactory and the control
loads are very light. There is no appreciable change in control
forces with different flap positions. In straight glide and turns
the glider handles similarly to an orthodox aircraft of corresponding
light wing loading. The flaps go down in approximately 10 seconds
and take slightly longer to move up. The flaps will not come up
fully but stop slightly out of the wing with the flap about 7½
degrees from fully up position. Check tests have, however, been
made with the flaps fully retracted by screwing them up into the
up position and no noticeable difference was observed in either
the handling characteristics or stalling speeds between these
tests and with the flaps slightly down.
Approach and landing
Suitable approach speeds are 65 mph ASI flaps up and 55 mph ASI
flaps down. The flaps are very effective when used to control
the glide path. There is very little float with flaps down. At
72 mph ASI (Max permissable speed with flaps down) the glide path
is very steep and height is lost rapidly. Side wind landings at
more than 5 - 7 mph should be avoided because of the difficulty
of balancing the wings on the central skid. All landings should
be made nose well up with the wheel back, in which position the
landing is easy and normal, flaps up or down.There is no tendency
to nosing over. Touch-down with the nose down is likely to result
in bouncing.
There is lots more but Robert Kronfeld finishes with his conclusions:-
"In spite of its unorthodox design the aircraft handles similarly to other light gliders with very light and responsive controls and is safe to be flown by service pilots in all normal attitudes of flight". so it is strange that when Captain Eric Brown. who was an extremely experienced test pilot flew it, he found such poor harmony of controls.
"I first flew RA809, towed by a Miles Master 11, on 22nd February 1945. For take off the flaps were locked up and the aircraft remained on the trolley with the control wheel held central until sufficient speed was attained for it to become unstuck by itself, avoiding any temptation to haul the glider off.
Once airborne, the glider was climbed quickly through the tug's slipsteam to take up a position above the tug. Towing speed was 110mph, and at this speed the elevators were extremely sensitive; if elbow rests had not been provided it would have been rather tiring to handle. The ailerons and rudders were somewhat ineffective, with an appreciable lag between application and effect.
After casting off from the tug I set up a glide speed of 70 mph, and it was noticeable that in any bumpy air there was a tendency to Dutch Roll, but there was no impression of any instability. The flaps could be lowered at 70 mph and the speed reduced to 60 mph, and they were effective in controlling the glide path.
For landing I learned to set up an approach speed at 70 mph with a tendency to overshoot, and then lower the flaps on approaching the airfield boundary. Holding off required a gentle touch to bring about a stall touchdown on the tail end of the landing skid.
This scale model revealed poor harmony of control, with a particular
sensitivity fore and aft which coupled with the indifferent view
from the cockpit, made the glider a touchy proposition for landing
in confined spaces. The thought of a medium tank appended to it
makes the mind boggle. It seemed a good idea at the time but..."
From "Testing for Combat" by Capt Eric Brown, Published
by Airlife Publishing Ltd.
