PZL I-22 Iryda. Part 3. 1985.Last change: March 2020
271b Section 1985-03-05
PZL Iryda I-22
Combat training aircraft.
Construction. Part 3.
Rescue system of the I-22 M-91 Iryda aircraft. 1989 year.
The philosophy of one decision.
One of the modern solutions of the aircraft is the crew rescue system. The basis of the system are two ejection chairs VS-1 BRI of the Czechoslovak construction used on L-39 aircraft. These are two-stage seats. The first stage is a telescopic tube that extends after firing a powder cartridge placed in a 38 mm diameter shell. The second stage is a powder rocket engine, located under the seat pan and operating for 0.2 seconds. On the I-22, however, a different strategy was adopted than on the L-39. It is based on the "one decision" philosophy. After making the decision to jump, the pilot grabs the handles placed on the seat bowl and pulls them. Everything that follows is done automatically and there is no need to perform additional activities.
The cab cover is not discarded. It has been assessed that rejecting the cover, which is sometimes unreliable, increases the time it leaves the machine. The aircraft I-22 detonated glass crushing was used. At that time, the glass crushing system was already used on combat aircraft of the Western countries, but in the Comecon countries it was the system used for the first time. A miniature fuse with a very small cross-section is pressed into the glass. It is arranged in characteristic zigzags, the course of which has been determined on the basis of dozens of tests. The fuse starts with a double electric igniter, which is activated from its own power source and even a complete failure of the power supply system in the aircraft does not affect its use. Firing the fuse crushes the glass into small pieces, moving them away from the cabin and clearing the path for the pilot in the chair. The thrown airman has a back parachute, parachute oxygen cylinders, emergency containers and, if necessary, inflatable vests and lifeboats. The emergency reservoir includes an emergency radio station, activated automatically during ejection.
Detonative glass crushing improves catapulting safety especially in unusual aircraft positions. A small profit on time is an increase in the chances for the pilot's parachute to unfold correctly, when jumping from a low height.
Despite the certainty of the glass crushing system, the designers assumed the possibility of "failure in failure". Therefore, if the glazing was not broken, the reinforced headrest of the chair will break the glass and allow the pilot to go with the chair.
After the seat with the pilot gets out of the plane, the second stage of ejection, i.e. the rocket engine of the chair, starts. The pilot seat rises 50-70 m from the flight line. At the highest point, the remote control automatically separates from the seat and the pilot's parachute opens.
The detonation system of the cabin glazing was a great unknown to our designers. It was not known what powder material to use, its amount, arrangement, impact on the crew, weather conditions and aging processes. No manufacturer or user publishes this information. The purchase of a license or know-how was out of the question. The problem was positively solved by engineers from the Military University of Technology and the Institute of Organic Industry. Specialists from the Research and Development Center of the Car Factory in Warsaw provided a lot of help. Test stands were installed at the Experimental Plant of the Institute of Aviation.
Much time and effort was devoted to research on how detonation of the fuse affects a person, after all, an explosion occurs a few centimeters above the aviator's head. He has a helmet, aperture and oxygen mask, but it was not known how the shock wave would work. Various animals were placed under the detonating cover; rats, rabbits, pigs and dogs. Some of the animals were dissected and the others were subjected to longer observation. The whole research was supervised by the Military Institute of Aviation Medicine. Each failure forced designers to change.
The whole long cycle of research had to end with a human trial. The stuntman from the Polish Film Jacek Kadłubowski took the place in the experimental cabin. He underwent appropriate medical examinations before and after the rehearsal. Mr. Jacek after the test said that the money he receives was earned the fastest and safest in his life.
It should be added that work on the rescue system was conducted in the light of two principles; the system is to be reliable and safe for the crew and the tests must be as low-cost as possible, which was the norm at the time. The testimony of savings is the fact that the test stand mounted on the Lim-2 was created by modification from a model of the I-22 cabin, made for the assessment of the preliminary design of the aircraft. Because it was necessary to use a functional new thrown chair for tests, it was the most expensive element in the tests. There were no other chairs. Under normal conditions, the pilot after firing and separating from the chair falls on his own parachute, and the chair falls to the ground damaging in a collision with the ground. Therefore, specialists from the Aviotex Plant in Legionowo developed a recovery system for the chair. The armchair received its own parachute and after separating from the dummy falls on this parachute. The system passed the exam and helped to reduce costs.
Because the VS-I-BRI chair guarantees rescue at speeds above 150 km / h, it was decided to perform comprehensive tests; crumbling the cover, throwing out the chair with the mannequin. The tests were decided to be carried out on the ground, because it gave the limit values, i.e. a minimum speed of 150 km / h and a height of 0 m. But where can you find a vehicle that will accelerate the entire cabin and maintain a speed of 150 km / h? Initially, attempts were made to set the test stand in the exhaust stream of another aircraft. However, this was troublesome and difficult for the surveyors.
It was more reasonable to place the test stand on the back of another aircraft. The Air Force has handed over a well-worn MiG-15 UTI. And these tests were not without surprises. Already during the first ride, the aircraft with the test bench very quickly reached a speed of 150 km / h, and the engine was running at minimum revs. This caused the generator not to start, which was to provide electricity for cameras filming the test. Therefore, a braking parachute was added behind the aircraft, which forced the engine to work at higher revs. The tests were successfully completed and put into serial production. The tests were managed by the head of the Flight Research Institute of the Institute of Aviation, MSc. Władysław Wyszyński. Ultimately, the PZL I-22 rescue system was refined and successful.
Written by Karol Placha Hetman