Jan Zurakowski:
Test Flying the Arrow. pg5

continued from page 4,

An engineer was instructed to write the specification for wheel brakes for the Arrow. The standard specification at the time, if I remember correctly, required brake capacity to have kinetic energy absorption equal to 1.2 times stalling speed squared, multiplied by the aircraft landing weight. Checking by phone, he got his figures, but the stalling speed quoted was completely unrealistic for use in estimating landing speed. Wings of 60deg delta reach stalling speed at an angle of attack of about 45 deg; during landing the geometry of the undercarriage does not allow the use of more than about 15deg.

     The specification went to the subcontractor and after the necessary design, development and proving time, the brakes were found to be completely inadequate for the aircraft when the wheels arrived, specially since in the meantime the aircraft weight was increased. A crash programme to develop new brakes was required to prevent delay in the flight testing.

     The Flight Test Instrument Section was developing a system known as telemetry, which would provide in-flight information consisting of a large number of parameters transmitted automatically to the ground. This system increased safety of the flight, helped to warn the pilot if he was approaching a limiting stress or other limiting conditions, and could be of high value if an aircraft crashed or disintegrated in unknown circumstances.

     With the help of an IBM 704 computer, a flight simulator was created using as many parts and systems from the aircraft as possible. Designers were very optimistic, promising to teach the pilots to fly the Arrow. Unfortunately the simulated aircraft was very difficult to fly; I lost control of it in three seconds; Spud Potocki, who was much better on instrument flying, managed to fly eleven seconds before crashing.

     I was completing taxiing tests in preparation for the first flight on an actual Arrow Mk. I. An unpleasant situation was created: if the simulator is unflyable, is the aircraft safe for flight? A specialist from the U. S. was called to assess the situation, but was not very optimistic.

     What next? To develop this simulator to flyable condition, or to fly the actual aircraft? I recommended disregarding the simulator for the time being and going ahead with the first flight. It turned out later that there was much more to the art of simulating flight than just feeding parameters into a computer and transmitting the results into cockpit instruments.

     The first flight of the Arrow on 25 March 1958 was very simple. Just check the response of controls, engines, under­carriage and air brakes, handling at speeds up to 400 knots, and low speed in a landing configuration. There certainly was more excitement for the several thousand Avro employees watching my first flight than for myself seated in the cockpit trying to remember hundreds of do's and don'ts.

     The aircraft flying characteristics were similar to that of other delta wing aircraft like the Javelin or Convair F-102, but the Arrow had a more positive response to control movement. The unpleasant part of my first flight was the feeling of responsibility, combined with the realization that the success of this aircraft depended on thousands of components, especially electronic and hydraulic, with only a small percentage under my direct control. But total responsibility for the flight was mine.

     Flight by flight, with ground monitoring based on telemetry results, I was going a bit faster and a bit higher. On flight No. 7, climbing at 50,000 feet, I exceeded 1000 MPH, and that was the only performance released at that time by Air Force headquarters.

     Phase One of the Arrow flight test programme was successfully completed, and F/L Jack Woodman made a familiarization and initial assessment flight. In August of the same year I started tests on a second prototype (No. 202) and in September on the first flight of the third prototype (No. 203), 1 exceeded the speed of sound.

     Shortly after, Prime Minister John Diefenbaker in a statement released to the press declared that two Canadian bases for U. S. Bomarc missiles would be established and the current development programme of the Arrow and Orenda Iroquois engines would continue, but would be reviewed in the next March.

     Development flying was speeded up when Spud Potocki and Peter Cope joined in testing. For me, the time to retire from testing had arrived. Normal retirement age from high speed flying was 40, and I was already 44. 1 was leaving experimental flying in good hands. Spud Potocki, Peter Cope, and F/L Jack Woodman were all excellent pilots, already with some experience on the Arrow. I moved to Engineering Division as staff engineer. Spud Potocki did the first flights on two more Arrows (No. 204 and 205), increasing the number of test aircraft to five. Testing was progressing well, but was slowed down by two accidents.

     I was involved in the first one. During a landing run on 201 I suddenly realized that the aircraft was pulling to the left and I could not maintain direction. Suspecting that the braking parachute had not opened evenly, I jettisoned it: there was no improvement, and at about 30 MPH the aircraft left the runway and the undercarriage collapsed in the soft ground.

     On investigation it was established that the left under­carriage leg had not completed the lowering cycle and during the landing run the wheels were at about a 450 angle to the direction of travel, producing a higher drag than the brakes on the right side could compensate for. With decrease of speed, rudder effectiveness decreased and the aircraft could not be prevented from changing direction.

     This accident probably could have been avoided if the warning light had indicated that the undercarriage had not locked properly, or if the chase plane pilot had watched me during landing and reported the trouble by radio. Unfortunately, he was short of fuel and landed first. If I had known of the fault, I could have landed slightly across the runway, making correction for the expected turning moment.

     The second accident took place on aircraft No. 202, flown by Spud Potocki. During a landing roll all four wheels skidded and the tires burst. The pilot lost directional control and the aircraft ran off the runway, damaging the right undercarriage leg. The initial impression was that it was pilot error. The pilot was thought to have applied too much braking pressure too early and locked the wheels.

     As I mentioned before, we had the telemetry system recording basic parameters of flight. It was recorded that during touchdown the elevators suddenly moved full 300 down.

     Spud was sure that he did not move the controls. Instrumentation experts suspected an error in recordings. Fortunately, a photograph of this landing run was discovered in the possession of a suspected spy, showing the elevators fully down. Now the cause of the accident was clear. The Arrow's elevators were large and when deflected fully down, acted as powerful flaps, increasing wing lift so much that only 20% of the aircraft weight was on the main wheels. The pilot was not aware of this and normal application of brakes locked the wheels.

     During this landing, a small aircraft vibration as the wheels touched the ground had resulted in a wrong electrical signal to the stability augmentation system, calling for full elevator down.

     The pilot was lucky; if the elevator had moved fully down in flight at any speed faster than 300 knots, disintegration of the aircraft was likely in a fraction of a second.

     Performance results collected on flights of five Arrow Mk. I aircraft fitted with Pratt & Whitney J-75 engines were used to estimate the performance of Mk. 11 Arrow fitted with Iroquois engines. The Arrow with J-75 engines was heavier than with Iroquois and had to be ballasted for a correct centre of gravity position, Mk. II with Iroquois engines did not need ballast and was about 5000 lbs lighter, and had 40 to 50% more thrust. It was estimated that we had a high chance of beating the world speed and altitude records held at that time by the United States.

     The first Mk. II (No. 206) was expected to fly at the end of February 1959.

     On 20 February 1959, the President of the Avro Company informed all working personnel over the public address system that the Prime Minister had just announced the termination of the Arrow and Iroquois programmes.

     A telegram received later in the day by the company instructed: