MTSU Diamond Fleet Operational Again After Hailstorm

Under the category of 'big surprises' ANN is pleased to learn that the formerly dour prognostications over the future viability of a number of aircraft hammered by a recent hailstorm ain't quite as bad as we feared. Following that sudden and severe hailstorm of October 17, 2011 that impacted all but three aircraft in Middle Tennessee State University's (MTSU's) fleet of 20 Diamonds and 5 Pipers, we're told that all but 4 Diamonds have been returned to service with the remaining 4 aircraft to follow within a few days.

"There was much public consternation and speculation about the extent of damage and repairability of the all-composite Diamonds," said Peter Maurer, President of Diamond Aircraft.

"From experience, I had a feeling that this would not be nearly as bad as was being speculated. The composite construction is very tough and resilient and even the relatively light carbon sandwich construction of the wing skins performed extremely well.

There were only two outer skin penetrations, limited to the area of the spars, where the skin panels could not deflect to absorb the impact of the golf ball sized hailstones, but these damages are easily repairable."

"We commend MTSU for prioritizing safety and taking a conservative approach by grounding their fleet, but with 400 students in the program, we knew they needed a very quick solution," continued Mr. Maurer. "That is why we immediately dispatched our experts to assist MTSU in assessing the damage, airworthiness and repairability of the Diamonds."

"The bottom line is that the Diamond airframes suffered very little damage in comparison to the metal aircraft and the minimal structural damage that did occur was quickly repaired," said Dr. Wayne Dornan, Chair of the Department of Aerospace at MTSU. "In comparison, the metal aircraft are going to be AOG for an extended period pending repairs, while the Diamond fleet is again fully operational," said Dr. Dornan.

The key points are:

1. While there was much superficial cosmetic damage from hailstone impact, all but 4 aircraft could be returned to service without repair, with cosmetic damage to be addressed when convenient.
2. One aircraft suffered a cracked canopy, which was repaired pending permanent replacement.
3. Three aircraft required relatively minor repairs to damaged wing skins, with full cosmetic refinishing deferred to coincide with scheduled maintenance.

Diamond's aircraft are produced from a low temperature curing epoxy resin / glass and carbon matrix versus the high temperature curing pre-preg composites typically used by most other composite aircraft manufacturers. This reportedly requires much simpler inspection techniques and much easier in-field repair and return to service.

With composite aircraft construction becoming ever more common and frequent questions about the inspection and repairability of composite airframes, this incident is a very significant and practical demonstration that attests to the toughness, durability and in-field repairability of Diamond's composite construction. 

Not only does composite construction allow aerodynamically more efficient design, the same properties that make the composite structure so tough and strong, also provide benefits when it comes to long term durability, overall structural integrity and crashworthiness.

FMI: www.diamondaircraft.com, www.diamond-air.at, www.mtsu.edu/aerospace