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June 1, 2003
By Barry Schiff
It is said that the de Havilland DHC-1 Chipmunk looks the way an airplane should look. Designed as a military trainer, the "Chippie" has a tapered wing and a narrow, sleek fuselage that give it the appearance of a petite World War II fighter. It also has that distinctively shaped vertical fin, the signature of many de Havilland designs (including the D.H.98 Mosquito fighter/bomber).
After World War II, de Havilland Aircraft of Canada wanted to develop an airplane for use in the Canadian bush. The parent company in England preferred instead that its Canadian counterpart first develop a replacement for the Tiger Moth, an open-cockpit biplane that had been the mainstay of the Royal Air Force (RAF) and Royal Canadian Air Force (RCAF). The Moth had become too antiquated to continue as a basic trainer. (The parent company was preoccupied with the development of the Comet, the world's first jetliner.)
The prototype of the Chipmunk first flew in Canada on May 22, 1946. Production aircraft were subsequently built there and in England (with some also built in Portugal). There is no significant difference between the Canadian and British models except that the last of the Canadian aircraft have bubble canopies while all others have greenhouse canopies like those on the North American T-6 Texan.
The Chipmunk is all metal except for the control surfaces and the rear two-thirds of the wings, which are fabric covered.
The DHC-1 designation indicates that the Chipmunk was the first original design of the Canadian firm, which eventually was allowed to develop its bush plane, the DHC-2 Beaver. De Havilland built 1,283 Chipmunks from 1946 through 1961, a 16-year production run, and the Chippie served the RAF longer than any other trainer. But time and technology caught up with the Chipmunk in 1971. The RAF began to replace its beloved trainer with British Aerospace Bulldogs, offspring of the Beagle Pup.
Currently there are 350 airworthy Chipmunks in civilian hands, of which 100 are in the United States and 138 are in the United Kingdom. The remaining aircraft are scattered worldwide.
The DHC-1 shown on these pages is the pride and joy of Robert "Chipmunk Bob" Hill, a Web developer for Nordstrom department stores. Hill grew up in aviation — his father was a naval aviator — and had always dreamed of owning an inexpensive, relatively simple warbird. He sought but could not find a Bulldog in good condition.
During his search, Hill obtained a taildragger endorsement in a Maule MX-7-180 and fell in love with that kind of flying. This redirected his search to include airplanes with tailwheels. The de Havilland DHC-1 Chipmunk seemed to fit the bill perfectly. He found one on the Internet and bought it on his birthday, December 29, 1999, for $40,000. He estimates that it is now worth about $55,000.
Hill's Chipmunk, WK639 (a serial number provided for the aircraft by the British Ministry of Defense), was manufactured in June 1952 in Chester, England, and was assigned to the RAF's University Air Squadrons, groups similar to the Reserve Officers' Training Corps (ROTC) in the United States. In 1971 it was assigned to active duty in the RAF to provide military students with the basic training needed to move up to a British Aircraft Corporation Jet Provost.
N6540C is based at Bremerton National Airport in northwest Washington State and is essentially the same as when it left the air force except for the addition of strobe lights and civilian avionics. The red, white, and blue roundel painted on the wings and fuselage is a postwar Type D insignia used by the RAF.
Hill says that he has no problem with maintenance or finding parts, although fixed-pitch propellers for the Chipmunk are becoming scarce.
The Chippie is powered by a 145-horsepower version of the 1930s-vintage, four-cylinder, inverted in-line Gipsy Major used in the trainer it was designed to replace, the de Havilland Tiger Moth. Manufactured by de Havilland, Bristol-Siddeley, and Rolls-Royce, these engines have a TBO of 1,500 hours even though the military ran them to 2,250 hours without difficulty.
The Gipsy Major also is called the "Dripsy Major" because if it isn't dripping oil, something is terribly wrong. It typically burns 1.5 quarts per hour (most is blown out), and 2.5 quarts per hour is the maximum allowable. "The fuller the oil tank, the more oil gets blown out," says Hill. He operates with only a half-full oil tank for local flights.
The Chipmunk has a 30,000-hour airframe, and Hill's airplane has only 11,800 hours, but this has been raised to an effective 21,000 hours because of its aerobatic history.
The airplane does not have a baggage compartment per se, but a cubbyhole behind the rear seat accommodates 40 pounds of personal items.
The brass, screw-in fuel cap for each of the two wing tanks looks more like something you would expect to find on a boat. A fuel gauge adjacent to each fuel cap can be read from the cockpit. Unfortunately, it is not illuminated, which restricts the Chipmunk from flying at night (but only in the U.K.). Each gauge has two scales, one for indicating fuel quantity on the ground with the tail down and the other for indicating fuel remaining in level flight.
The Chipmunk does not have a primer in the cockpit like most airplanes do. This requires the pilot to undertake a quaint priming ritual before engine start. It involves either opening the left side of the cowling or accessing the priming controls through small circular ports cut out of the cowling. The index finger of the right hand is used to pull a ring that opens the carburetor, and the left index finger moves a lever up and down to manually pump fuel into the carburetor until fuel drips onto the ground from the overflow vent at the bottom of the engine. This done, the propeller is pulled through four compression strokes to suck fuel into each of the four cylinders.
Although there is no electric fuel pump, there are two engine-driven fuel pumps.
Hill and I are large pilots, but we are comfortable in the narrow cockpit, which has the fit and feel of a fighter. Both pilots are surrounded by controls and switches that fall easily to hand. You have no doubt that this is a military machine.
Although the seats are not adjustable, the rudder pedals are, moving fore and aft to accommodate long- and short-legged pilots. Solo flight is allowed only from the forward cockpit.
A sliding knob on the floor near the base of the control stick is the "fuel cock." It moves fore and aft to open and close the valve, supplying fuel from both wing tanks to the engine. Ahead of that (also on the floor) is the horizontally mounted, British-style compass that is so large that it looks as though it belongs on the bridge of an ocean liner.
Another interesting instrument is the bat and ball, the British term for a turn-and-bank indicator. A spring-loaded push button on the left electrical panel is used to tap out Morse code via the yellow light on the Chippie's belly to communicate with others in your formation.
There are two magneto switches in each cockpit, and all four must be flipped up to start the engine. Only the front cockpit has a starter button.
Throttle cracked and mixture rich (meaning that the mixture control is fully aft, another British tradition), and you're ready to start.
Chipmunks in military service literally started with a bang and the smell of cordite from an exploding 12-bore shotgun shell (minus the lead shot), a part of the Coffman cartridge-type starter that uses rapidly expanding gases to turn the crankshaft. Most civilian aircraft have been converted with electric starters.
Hill's Chippie starts after only two blades. Power should not be applied for taxi, however, until the oil temperature reaches 40 degrees Celsius.
The tailwheel is fully castoring and non-steerable, which means that differential braking is used to maneuver on the ground. But it is unlikely that you have ever used a brake system like the one in a Chipmunk.
You pull aft on a parking-brake lever (similar to the parking-brake handle on some cars) on the left side of the cockpit to engage a ratchet at the point where the disk brakes barely rub against the wheels. The ratchet then holds this slight amount of braking without your having to pull on the brake handle. After that, moving the rudder bar (pedals) determines the wheel to which the braking applies. In other words, move the right rudder pedal and brake pressure is applied only to the right wheel, and so forth. When taxiing with a crosswind, add another notch of brake and apply downwind rudder to keep the Chippie tracking straight. A new Chipmunk pilot tends to overcontrol, but with a little practice, he discovers that the system is effective and can be operated without having to think about it.
On the right, a lever similar to the brake handle is used to operate the flaps. Lift it to the first notch for 15 degrees and to the second and final notch for 30 degrees.
Some S-turning is needed to see over the Spitfirelike nose.
The runup is conventional, and there is a perceptible sense of excitement as you line up on the runway.
The rudder becomes effective almost as soon as the throttle reaches its forward limit, and the tail comes up shortly thereafter. Pilots new to a taildragger without a steerable tailwheel quickly learn that the airplane must be "flown" with the flight controls from the beginning of the takeoff roll until the aircraft comes to rest at the end of a flight.
The Chipmunk lifts off at 45 knots, and your instinct will be to press the right rudder pedal as the nose pitches skyward. Do not do that in this airplane. The nose of a Chipmunk yaws right, not left, because British engines turn the "wrong way" (counterclockwise when viewed from behind) and require left rudder to keep the airplane on an even keel during full-power climbs.
Surprisingly, the engine is canted 4 degrees right, which exacerbates the right-turning tendency. This was done in an effort to better prepare pilots for transition into high-horsepower fighters.
The tachometer has two hands, one to indicate thousands of rpm and the other hundreds. It is similar in appearance to the adjacent altimeter, which can be confusing. Retard the throttle as you level off after a climb and you get a visual sensation that the airplane is losing altitude.
Maneuvering is the Chipmunk's strong suit. The controls are so exceptionally well balanced, light, responsive, and harmonized that the airplane could easily be the benchmark against which other lightplanes are measured. The DHC-1 is an absolute delight to fly, and you quickly feel as though you are at one with it. Some pilots, however, find the rudder to be too sensitive and learn to press a pedal instead of shoving a foot into it. The airplane does not tolerate a ham-fisted pilot. My friend Brian Souter says about de Havilland trainers, "They are easy to fly but difficult to fly well."
Aerobatics are allowed, but the engine will quickly burp and belch during negative-G maneuvers because it does not have an inverted fuel system. The Chippie is designed for plus-9 to minus-6 Gs.
There is no stall-warning indicator, but the strong prestall buffet serves the purpose. Although stalls can be sharp with power on and flaps extended, they are otherwise mild-mannered. (Wing camber increases from root to tip, and this helps to prevent the wing from dropping during a stall.)
4 Chippie does not tolerate being taken for granted, though, and drops a wing in protest to those who don't keep the slip-skid ball in its cage. Using ailerons to pick up a stalled wing can aggravate the roll. As a matter of fact, it is recommended that a pilot use opposite aileron to assist in spin entry. Chipmunk pilots claim that it is as easy to avoid an inadvertent spin as it can be difficult to recover from one. A placard in the aircraft says, "Spin recovery [from a fully developed spin] may need full forward stick [emphasis mine] until rotation stops."
The Chipmunk's only serious shortcomings are endurance and range. With a total of only 22 gallons of avgas in the tanks, you are effectively limited to two hours and 200 nautical air miles (plus a 45-minute reserve). Retard the throttle for descent and a pawl mechanically pulls back the adjacent mixture control into the rich position. This makes it impossible to make an approach and landing with a lean mixture.
The carburetor heater does not really heat the induction air. Instead, the carburetor uses ambient warm air from inside the cowling. The RAF wired this to the open position. Although this diminishes performance slightly, it helps to prevent students from learning about carburetor ice the hard way.
The canopy may be slid back to the first notch (a few inches) at any airspeed, but open it to the second notch (a few more inches) and the maximum-allowable airspeed is 90 knots. During approaches on warm summer days, however, many pilots open the canopy all the way for a dose of delirious joy.
The Chipmunk glides best at 60 knots and is slowed to 55 over the threshold. Most pilots land with 15 degrees of flaps, but using 30 improves over-the-nose visibility. Slips are a joy because there is hardly any airframe buffeting and control forces are so light.
The Gipsy Major should be idled for a few minutes before shutdown to allow engine temperatures to stabilize. Then shut off the magnetos and advance the throttle fully forward to prevent backfiring and "dieseling."
As the propeller ticks to a stop, a new Chipmunk pilot usually just sits in the cockpit for a while wearing a smile that reveals his infatuation. The Chippie engenders that kind of affection from those lucky enough to fly one.
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