T-34C Crash Report ~

After watching the dead stick crash landing video you might be wondering what damage was inflicted on the airframe. The FAA and NTSB investigation revealed the following:

Nose Gear:

As witnessed, the nose gear took a great deal of the impact energy and suffered the worst for it. We built our gear to handle a 55 pound model, and luckily the T-34C only comes in at 30 pounds. This purposeful over-engineering allowed the gear to bend under the significant impact loads and not break. If landing gear break, the excess impact energy is immediately transferred to the airframe (say good-bye to your cowl). We were very pleased with the gear's ability to withstand the impact force. Damage was limited to the bent fork and lower strut, the down-lock was bent as was one of the upper links. Replacement parts will be available for our gear and in this case, the parts cost about $30.

The nose gear retract mounting rails and supports were not damaged, nor was the cowl, spinner or prop (whew, that was a $55 prop!).

 

Now how about the fuse? At first we did not see any damage, but a closer look did reveal some slight damage under the clamshell hatches (upper rear of the cowl). After we realized the Moki 2.1 just was not going to give us the power we need (at 6000' ASL) we were in the process of relocating the firewall aft and it was then that we discovered some small stress cracks in the foam. The pictures below show the area under the clamshell doors. Where the cracks occurred we drew a line with a thick black pen. The cracks were 1-1.5" deep. You will also see several empty cavities bored out in the foam - these were made to accommodate radio gear such as switches, wiring, air tank fill valve, retract servo, batteries, fuel lines and the RX. We put all this gear up front anticipating the need for forward weight for CG balancing only to find that all that gear needed to be placed further aft (thanks to the Turbo Mentor's generous nose moment). The gear was relocated to the rear baggage door and wing saddle and these cavities were left empty which did serve to weaken the fuse in this area and probably contributed to the damage. The fuel tank cavity is located below this equipment "floor" and further served to reduce the foam mass in the area.

The repair was a simple application of Gorilla glue. Zap A Gap or epoxy would work too, but we thought the expansive nature of the polyurethane would do well to find the air gaps and bind everything up. Additionally, we filled the gear cavities with EPP blocks. Since the firewall was going to be relocated 2" aft to accommodate the new gas engine (Revolution 50) we also had to relocate the plywood keys that serve to grip the firewall and extend back into the fuse. We came up with a better design than before which incorporates two upper keys (there will also be two lower keys) that extend back over the gear area. These 3/16" ply plates will help to reinforce this area.

How about the rest of the plane?

Even with the significant flex in the aft fuselage there was no damaged to the underlying foam or to the polycarbonate skins. Placed under pressure the aft fuse and tail assembly feel as solid as they did prior to the accident. The wing also showed no signs of damage or stress despite its considerable flexing during impact. The main landing gear retracts and its mounts also had no damage.

Overall, we are quite pleased with the extent of the damage (actually the lack of damage) and we believe this is evidence of the resiliency of the construction materials and assembly technique.

The NTSB has cleared all repair work and approved the installation for the new power plant (which fits completely within the cowl). However, the NTSB did suspended the pilot for his actions in the cockpit. While not obvious in the video, the pilot while on final dropped his lucky rabbit foot on the cockpit floor and was bent over trying to recover it and wedged himself under the instrument panel during the moments of touchdown (that's why you can't see the pilot in the video). These moments of inattention, the NTSB concluded, caused the aircraft to have excessive approach speed and sink rate that lead to a violent bounce and resultant contacts with the runway. Pilot was hospitalized for his injuries - appearently the lucky foot was not that lucky....

 

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