N595DYCzech Sportplanes Sro DYNAMIC WT9 · 2009

On January 9, 2011, about 1535 Pacific standard time, a Czech Sportplanes SRO, Dynamic WT9 light sport airplane, N595DY, landed hard at Palm Springs International Airport, Palm Springs, California. The student pilot was operating the airplane under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91. The pilot was not injured, and the airplane sustained substantial damage to the left horizontal stabilizer and left aileron. The cross-country personal flight departed Marana Regional Airport, Tucson, Arizona, about 1300. Visual meteorological conditions prevailed, and no flight plan had been filed.

The pilot reported that during the final approach the airplane encountered a strong downdraft. As he attempted to recover control, the airplane's canopy opened, and extended to the full up position, such that he was unable to reach the handle to retract it. The airplane descended rapidly, and he applied full throttle in an effort to arrest the descent. As he approached the runway threshold he reduced engine power, the airplane descended rapidly, and landed hard. The airplane then departed the runway, coming to rest in the adjacent gravel verge.

The composite airplane was equipped with a tip-up canopy, hinged at the forward cabin area, aft of the firewall. The canopy was locked in the down position by a single longitudinal spring-loaded latch pin, located in the center aft section of the canopy, above and behind the cabin seats. Lateral canopy support in the down position was provided by a set of two guide pins, which slide into slots in the aft cabin frame pillars. A set of gas struts were incorporated into the canopy frame to assist with raising the canopy.

Examination of the airplane by the National Safety Board (NTSB) investigator-in-charge following the accident revealed that the latching pin, in the locked position, extended 15 millimeters beyond the canopy frame. During the examination, the latch was cycled in and out by hand, and it was found that the pin would intermittently extend 5 millimeters short of the full travel. The pilot stated that the latch was fully extended prior to departure. No damage was noted to the striker latch pin or guide pin striker plates. The airplane was not equipped with an audio or visual lock indicator.

The airplane's manufacturer issued Mandatory Service Bulletin ZBTWT9 10A/2008 on October 23, 2008. The Service Bulletin addressed a series of operational updates, requiring a revision to the flight manual. The revision stated that the pin extends between 8 and 12 millimeters when locked, and if the pin is not securely latched during the pre-flight inspection, the canopy could open in flight. The revision included operational updates specifying procedures for securing an inadvertent canopy opening during various phases of flight. The procedures stated that provided the airplane is flown in a straight and level attitude, the canopy will only partially extend, and can be retracted and locked by hand. The update included the following warning:

"During side-slipping flights with partial cockpit canopy latching (incorrect turn – slipping turn, skidding turn, and side slipping for landing) due to asymmetrical flow over fuselage by the air flow, the cockpit canopy will be carved through the gap and subsequently will be full open by help of the gas struts. The cockpit canopy will become the braking shield, what will cause abnormal airplane descent due to increased total drag."