Flight test: DHC-1 Chipmunk T.10
- Credit: Keith Wilson
First flown in 1946, the charming Chipmunk outlasted more modern designs and continues to serve with the RAF as an indispensable tailwheel trainer for BBMF pilots
Words: Bob Davy Photos: Keith Wilson
This year is the 75th birthday of the DHC-1 Chipmunk and to mark the occasion we decided to flight-test a particularly special example, G-BBMN. Formerly WD359, it was owned for many years by the founder of the Chipmunk club, Ralph Steiner and once flown by WWII fighter ace Adolf Galland. Ironically the Chipmunk was the platform for selection and basic training of British military aircrew for nearly fifty years after WWII, which is maybe why Adolf wanted a go in it.
It’s difficult to convey the sense of drama experienced by a young pilot trainee−having put on RAF-issue flying suit, parachute, boots and bone dome−to stride (or waddle) across the apron at a military airfield and climb into a military aircraft for the very first time, then sit in the cockpit looking across a wing bearing roundels. From the 1950s until the 1990s, that first military aircraft would invariably have been a Chipmunk. Forty years ago, the experience was mine, and I can still remember it like it was yesterday.
The Chipmunk was only in production from 1947 until 1956, during which time nearly 1,300 were built−some in Canada and under licence in Portugal, but mostly in Britain at Hatfield and Broughton.
The RAF still operates two Chipmunks as part of the Battle of Britain Memorial Flight (BBMF) using them to train pilots going onto the Spitfire and, more specifically the Hurricane−an aircraft the Chipmunk is said to behave like in the circuit when loaded to the aft end of its C of G envelope. The BBMF’s Chipmunks are also used for transport, liaison and recce of new display sites.
In the early 1980s when I was in the RAFVR University Air Squadron system, one of the opportunities for cadet pilots was to apply for ‘detachments’ to operational squadrons, gain experience of service life and hopefully get a ride. My first detachment was to RAF Binbrook and I quickly found myself strapping into a Lightning. We started up, taxied out to the holding point, ‘went tech’−it means broke down−and then taxied back. Round two was at RAF Conningsby later in the year. This time it was a Phantom. We started up, taxied out to the holding point... went tech again and taxied back. I stayed on at the squadron for nearly a week, hoping that another opportunity might come, but it didn’t. In the end a pilot from the BBMF took pity on me and flew me in a Chipmunk for 25 minutes. The following week I puked my way round a three-ship formation of Jet Provosts at RAF Cranwell.
I don’t think I was appreciative enough of the Chippy ride.
An aircraft that looks right...
At first glance the Chipmunk is streamlined and ‘aerodynamic’. Some of the military colour schemes can be quite clunky but when stripped bare of adornment the aircraft’s lines are beautiful to behold. And yet despite its all-metal, stressed skin construction, it is most definitely a design from the first half of the twentieth, century rather than the second half. The nose profile appears almost identical to the earlier de Havilland Tiger Moth−no surprise there then, considering the aircraft came from the same stable and both have Gipsy inverted four-cylinder engines. In fact, a popular mod for Tiger Moths is to have a Chipmunk’s Gipsy Major retrofitted to them, increasing the power from 130hp to 145. The rear of the fuselage and tail look virtually identical to the de Havilland Mosquito. After escaping from Poland, where he had previously designed some very nice fighters, chief designer ‘Jaki’ Jakimiuk’s first job with de Havilland during WWII was helping to develop the Mosquito.
The Chipmunk wing is the most modern part of the aircraft, all-metal (albeit fabric covered aft of the mainspar) with a tapering section and squared tips. The control surfaces are metal-framed. Fuel is carried in two small wing tanks: just nine gallons per side, or twelve gallons per side for Canadian versions. The cast brass fuel caps on the wings and ‘clockwork’ indicator gauges hark back to another age, looking like they were taken from a Victorian boat. Google the word ‘steampunk’ and you’ll get the idea.
The cockpit is very 1940s−black on black, with a WWII RAF standard flight instrument layout and P-compass on the floor. When new, the Chipmunk came with a cartridge start system that used modified shotgun cartridges−I told you it was old technology−but almost every surviving Chippy has been retrofitted with an electric start after the cartridge system was found to overstress
Many Chippies have had engine retrofits: American flat-fours, sixes and even turbines but unfortunately most of them got a wave of the ugly wand. The one and only retro’ that does it for me is an in-line six from a Zlin. It’s got 180hp but, equally important, from the side it sounds like a Merlin.
To prime this aircraft’s standard Gipsy engine, I ask my ground crew to pull on the hoop at the end of a cable coming out from the left engine cover and then stick a finger in to operate the wobble pump lever until fuel flows out of a drain underneath the rear of the cowling. Ah, but I don’t have a ground crew, do I? So, I do it myself−and I also pull the propeller through and listen for a clunk: if it isn’t audible, the magneto impulse system has stuck, meaning the engine won’t start no matter what I do with it. A tap with a piece of wood normally fixes that.
- 1 Secretive UAV sighted?
- 2 EASA approves Skycharge electric aircraft charger
- 3 Flight test: Piper PA-23-250 Aztec
Back in the cockpit, I reach over my head to pull the canopy forward with the yellow handle at the front, then I reach down by my left knee and find the Air/Ground switch (that’s the battery switch−it’s a British military thing from the era). I flick it up, ask my rear seat passenger/student to flick up the two mag switches on the left cockpit wall in the back, then do mine which are situated in the corner between the left side of the front panel and left cockpit wall. I call ‘clear prop’ and push the start button on the right of the panel. (Different aircraft have the button in different places−the defunct original cartridge start button is on the cockpit wall next to my left elbow.) The old Gipsy lurches into life and settles down to a steady thrum. I check oil pressure rising within thirty seconds and remember to switch on the generator, then the radio, and wind the runway heading onto the P compass as a safety measure on a multi runway airfield. As soon as the oil temp comes up to 40˚C we can start to taxi.
It’s windy today so I’m going to preselect some wheel brake to help in the turns. I do this by setting the brake lever on the left cockpit wall by my leg. On the lever is a collar and if I press it downwards with my little finger as I pull the lever it engages successive teeth on a ratchet. Moving the rudder pedals to either extreme then engages the wheel brake on that side to the preselected amount to assist turning. Between two and four notches is usual. However, this also restricts rudder movement, so it’s important to unlock the brake lever from the ratchet before doing aerobatics, and particularly spinning.
Taxying is quite easy in a Chippy. The tailwheel is fully castoring and the combination of differential braking and an effective rudder means it’s always going where I want it to. That in-line engine makes for a rakish, slender nose and so the view out is good for a taildragger−except directly over the nose, obviously. I can already feel how light the stick and rudder forces are and unless I knew different, I would swear that everything is pushrod-operated, rather than done with cables and chains. There is absolutely no slack in the stick or pedals, neither in this aircraft nor in any of the previous examples I have flown.
The engine run up and vital actions are as straightforward as it’s possible to be−just remember to keep the stick back (not so vital in a nosewheel aircraft) and we are soon ready to take off. One stage of flap is used for the shorter strips but today we have 900 metres to play with, so we’ll take off clean and avoid one further catch in that I would need to retract the first stage by 93kt. (Second stage Vfe−flap limiting speed−is an ultra-low 71kt).
The takeoff is sedate by modern standards, with 145hp pulling 2,100lb. There is plenty of time to get something wrong and then correct it during the ground run, the occurrence-rectification interval depending on the experience and courage of the instructor. For a conversion flight, rather than ab initio training, the classic mistake is going to be pushing right pedal for takeoff rather than left−the low power-to-weight ratio means you can catch it in time if you get it wrong.
… and flies right
I do my best to use the correct pedal and open up the throttle with the stick hard back. Everything is happening in slow motion, so I push the stick forward and raise the tail then sit there bouncing sedately on the main wheels. At around sixty knots the Chippy decides it’s going to fly and I let it, with the tiniest of back stick. At seventy knots I transition into a climb, seeing 900fpm on a standard day with moderate temperature and pressure. As soon as we get airborne, I’m aware what a lovely aeroplane this is. I have a little play on the controls and quickly confirm my preconception that the Chipmunk has perfect handling.
There is no air-to-air photography today (we’ll do that later, with owner Steve Baker at the controls and me flying the camera ship) so I can get stuck in straight away and start enjoying myself. I had heard the old saying about the Chipmunk being easy to fly and difficult to fly well, and wanted to analyse that a little bit. For example, if I roll just with the stick alone there is some adverse yaw, albeit nothing compared with the Tiger Moth. If I coordinate with rudder and stick, I can get beautiful, balanced turns. In other words, a student can be ham-fisted and move the thing around the sky badly but it takes finesse and coordination to do it in balance.
I level off at 2,000ft and let the speed build before pulling the throttle back. 1,950rpm gives me a long-range cruise of 90kt, burning just over 7gph. Opening up to 2,050rpm gives 105kt, burning 9gph−quite a high fuel consumption for 145hp, but then the Gipsy Major has its roots in a WWI V8 aero engine. This was the Renault 8G, which was chopped down by Frank Halford to make an upright four-cylinder for the early de Havilland aircraft, and finally inverted for the DH.60G III Moth. The success of the DH.60 marked the beginning of light aviation in Great Britain but by the end of the 1940s the Gipsy Major engine was starting to show its age. However, de Havilland seemed to have a thing about it−seeing as the design was the company’s collaboration with Frank−and persevered with adding more cylinders and wringing out more power. Six-cylinder Gipsy Queen engines of 400hp were still being built at the end of the 1960s for the de Havilland Dove. In addition to power and vibration the other thing that the Gipsy produces is a prodigious quantity of carb ice and many Chipmunks fly with their carb heat lock-wired hot, the way the RAF did it.
I’m free of controlled airspace now and start a climb to 4,000ft to try some stalls, spins and aerobatics. As I’m climbing, I remember the 1980s again and a photograph that lived on the bedroom table of my RAF cadet pilot flat mate, surname Mustarde. It was a picture of his dad in the 1950s in a very baggy flying suit standing next to a pile of aircraft parts that used to be a Chipmunk. The story goes that he couldn’t get out of a spin and baled out, and after that−the eighth spinning accident−de Havilland fitted spin strakes to Chipmunks. (As an aside, Mustarde senior went on to have a successful flying career and once captained an airliner with a first officer Salte and flight engineer Pepper.)
I try a stall first. Close the throttle, select carb heat and concentrate on keeping wings-level and ball in the middle. Speed reduction is slow because she is slippery−no surprise there−and the balancing act to maintain height perfectly and keep the ball in the middle gets harder as stability reduces with airspeed. Then I feel some buffet and finally the nose drops at 45kt. I check forward on the stick, add a dash of power and wait until she flies again before I gently pick the nose back up.
Now I select one stage of flap−the lever is on the right side of the cockpit. To deploy it, just pull the lever back and let it engage a detent. To raise flap, squeeze the handle in the lever to release it from the detent and allow it to spring forward. Older readers and drivers of classic cars may realise I am describing a fly-off handbrake. With flap, the stall is something like ten knots slower−the ASI needle is oscillating so it’s hard to be specific. I check forward, add power, increase speed and finally retract the flap.
I’m back at 4,000ft and close the throttle again, maintain wings level, check the brake lever, let the speed come back below fifty knots then smoothly pull the stick all the way back and push on full right rudder. The Chippy drops its right wing and spins to the right−it’s quickly fully-developed and stays there, not turning into a spiral dive. To exit, I confirm throttle closed, change feet and push the stick all the way forward to the panel. The spin stops and I centralise controls. In one and a half turns plus recovery actions we lose just under 500ft.
I’m thinking the Chipmunk would be a nice aircraft to flick but it’s only semi-aerobatic and flick manoeuvres are not on the list. I’ve asked around and there are pilots who’ve done one accidentally−e.g., at the top of a loop, resulting in an impromptu avalanche−so yes, it does flick but no you don’t, for the same reason you don’t take your grandmother roller skating.
I do fly some basic ‘aeros’ though, starting with a loop at 120kt and 3G. Pulling up and keeping the ball in the middle with progressive left rudder, I add more throttle as the speed reduces. We sail over the top and down the other side, power coming off to stop the rpm exceeding 2,550rpm as speed increases. Stall turn next, so I keep the pull going through the bottom then up the other side again, centralise the stick as we reach the vertical with progressive left rudder, then full right rudder and left stick to counter the adverse yaw. The nose slices perpendicular through the horizon until we are facing vertically downward. I centralise stick and rudder and then simultaneously pull out of the dive while bringing the power back. Last one is a barrel roll: 120kt seems a good number to go for again, bearing in mind the Vne of 173kt. I pull up until I have the heels of my boots on the horizon then start to roll to the right, finding a plume of smoke from a power station on the horizon to roll around with that at my centre. All the time I am conscious to keep that ball in the middle, coordinating aileron with rudder and managing power. I have not had to think about control harmony at all and that means it must be perfect. What fun it is.
Oh, I didn’t mention the engine stopping, did I? At the top of the loop it coughed, which had my attention for a second or two. Also, at the top of the stall turn−in fact the engine completely stopped that time but came back again−and it did so at the top of the barrel roll as well. I found myself getting used to it and it didn’t bother me too much in the end, although owner Steve later told me he tends to do his aeros over airfields.
I’d better think about landing before I run out of fuel. Short-term parking fees for Chipmunks are zero at all airfields because they always have to be parked at the pumps. I pull that carb heat out again, aim for WD359’s home base at Denham, drop under the TMA with a flattened aileron roll and then fly at 1,000ft on a long right base to final, getting the speed below 93kt for first stage of flap, then back to 75kt short base, 65kt final with full flap and 55kt short final. 1,100 rpm gives 300fpm at this stage. I take two notches of brake preselect, cross the hedge at 50kt and manage to kiss the tarmac with no great effort then immediately push the stick forward to keep it there. 400 yards would be safe to land in, less with practice and there’s a lot more at Denham so I’m not braking yet. At White Waltham I used to have a Chippy at my disposal and sometimes played a game where I would use the brake lever aided by progressively pushing the stick to keep the aircraft wheeling as long as possible, until it felt like the tail was dropping to the ground at walking pace. Today though I just roll to a stop and save Steve another bit of brake wear. Like all pilots who have ever flown a Chipmunk, I love this aeroplane.
If I was a sprog trainee military pilot in the 1950s what would my colleagues and counterparts be flying? In the USA it would be the Beech T-34, which started replacing the T-6 Texan in 1953 - both thirsty aeroplanes and more capable than the Chipmunk, but at a cost. The Russians would be flying the Yak-18, but not the ‘18T - the four-seater that we all know today. The first Yak-18 was a fixed-gear tailwheel aircraft with a tandem cockpit, later replaced with a retractable tricycle undercarriage and a more powerful engine, the forerunner of the Yak-50/52. The Chinese flew the Yak-18 too, as the licence-built Nanchang CJ-5.
Other air forces jumped on the Chippy bandwagon over the years, some as late as the 1970s, when the RAF were getting rid of theirs and replacing them with Bulldogs; Belgium, Burma, Ceylon, Columbia, Denmark, Eire, Egypt, Ghana, Iraq, Jordan, Kenya, Lebanon, Malay, Portugal, Saudi Arabia, Syria, Thailand, Uruguay and Zambia. The Chipmunk ended up flying in more than sixty countries and also has royal connections: Prince Phillip (1952), Prince Michael of Kent (1962), Prince Charles (1969) and Prince Andrew (1979) all learned to fly on the Chipmunk.
Nearly half of all of the Chipmunks built are still flying - around 500 in all, a loyal band of dedicated owners polishing and touching up their incredible variety of military and civilian colour schemes, wiping oil off their bellies after every flight and fashioning aircraft-shaped drip trays (one thing more in common with the contemporary Lightnings and Phantoms). Prince Phillip’s aircraft, delivered new to White Waltham for his course in ‘52, is still flying in New Zealand. Talk about a life of privilege...
SPECIFICATION | DHC-1 Chipmunk T.10
Length 25ft 5in
Height 7ft 1in
Wingspan 34ft 4in
Wing area 172 sq ft
Weights and loadings
Empty weight 1425lb
Useful load 675lb
Wing loading 12.21 lb/sq ft
Fuel capacity 16 imp gal
Mk21/22 24 imp gal
g limits +6/-4
Vne 173kt (155kt in some flight manuals)
Stall, clean 45kt
Stall, full flap 38kt
Take off dist 450yd
Landing dist 350yd
Rate of climb 840fpm
Max range 300nm (24gal)
Engine and propeller
Gipsy Major 8/10 developing 145hp @ 2,550rpm driving a Fairey Reed metal fixed-pitch propeller