Loss of Canopy


Wayne Paul

May 25, 1996 started out like any other soaring day. A few hours in the office, checked the sounding, and then out to the Nampa airport. Nampa is located about fifteen miles west of Boise and is a popular basing location for many Boise aircraft owners. As a result there is a fair amount of general aviation traffic but today the traffic was light. The temperature was in the high 60s and forecast to get up to 75. Day was developing slowly and the winds were out of the northwest at 10-15 kts.

There were five of us getting ready to fly. Bob Gladicks and Glenna Doke had come down from Sun Valley; the rest of us were from here in the Boise valley. We assisted each other rigging our aircraft. Two ASW-20s, a Libelle, a Mini-Nimbus and my "T" tailed HP-16. Bob was first to launch in his ASW-20, followed by Frank Kruesi in the Mini-Nimbus and Stuard Larimore in his ASW-20. I was planning on being the last to launch because I wanted the day to develop a little more; however, Roger Frank was working on the Libelle's radio wiring so I became the next in the launch order.

I manned my HP and was pushed onto the runway for launch. Glenna assisted me with the hookup. This was her first time hooking a towrope to an HP. I gave her instructions from the cockpit and Glenna performed in her usual competent manner.

The initial takeoff roll was uneventful. The Cessna 182 with the tow pilot and his passenger slowly climbed as we progressed down the length of the runway. At about 200 feet we hit a thermal and the canopy popped open. There was a rush of wind. I reached for the canopy with my left hand. Before I could grab it the hinges on the right side of the canopy broke. The canopy was flailing around on the tether attached just aft of the instrument panel, which was used to limit how far the canopy would open. I pulled my head as far back as I could under the turtle back to keep the canopy from hitting my face. The tether broke and the canopy departed the aircraft. As I reached for the hook release, the towrope broke. My altitude was approximately 250 feet.

Now it was time to get this thing back on the ground! To get set up for a down wind landing I made a left turn banking 45 degrees, kept the nose down, maintained 50 knots. When I knew I had the field made I started lowering the flaps. Touch down was at 45 knots (55 to 60 ground speed) with the flaps at 90 degrees. The first part of the rollout was normal, until I lost aileron and rudder authority. The HP was rolling along at 20+ kts when this occurred. The wing dropped, brakes were applied and directional control was attempted with the steerable tail wheel. I was all over the runway before finally stopping.

I unstrapped, took off my chute and examined the aircraft. The canopy had hit the leading edge of the right wing and left a small dent. There was a small scratch on the right side of the fuselage. It was at that time I noticed my hat and glasses were also missing. The only injuries were a small bruise on my right arm and my pride.

The first questions ask was "how does it fly without the canopy?" Well -- there is a lot more noise. There was no significant change in control feel or authority. However, I really missed the yaw string.

Roger hoped that we could find the canopy. Maybe at least the frame could be salvaged (Wrong!) Shortly after clearing the runway a gentleman drove up in a pickup with what was left of the canopy and my hat. They had fallen in the grass next to the far end of the runway. When informed that my glasses were also missing he suggested that we go take a look. Within ten minutes I had my glasses. They were intact but in need of major adjustment.

The handling of this incidence was far from perfect. I distinctly remember closing and checking the canopy prior to being pushed into takeoff position. I remember unlatching the canopy to give hookup instruction to Glenna. I didn't actually open the canopy because it was not necessary for her the hear me. Again I remember moving the canopy handle to the closed position but obviously I did not do a security check.

I was distracted (to say the least) when the canopy came open. I remember a lot about what the canopy was doing but little about where I was with relationship to the tow plane. I remember reaching for the tow hook release; however, the tow rings were still attached when I landed.

Common knowledge items that would have prevented the incident:

  1. Briefing the ground crew on the unique characteristics of the HP-16 before it was manned and on the runway!
  2. Not allowing myself to be rushed by a change in launch order.
  3. Performing the complete checklist immediately prior to take off!
  4. When an emergency occurs, take time to evaluate the situation. (I was too anxious to get back on the ground. I should have had the tow plane enter the pattern's down wind leg so I could have made a normal approach!)

The incident precipitated the need for the following aircraft modifications:

  1. Make the hook release more unique and predominate.
  2. Change the location of the canopy retention strap to ensure the canopy does not hit the pilot if there is ever a need for it to be jettisoned.
  3. Modify the tail wheel installation to allow more control when aileron and rudder authority is lost.

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