NTSB Identification IA-AMW-FU2
Incident occurred Sunday, December 21, 2008 in Ames, IA
Probable Cause: Approval Pending
Accident Hangar: Skybox SR6060, registration N2516
Injuries: Loss of confidence in hangar heat system
Damage: Substantial
HISTORY OF FLIGHT
On December 21, 2008 at an unknown time, a Skybox SR6060 hanger, N2516, experienced total loss of heat generation in the main passenger cabin and lavatory on level 1, first class cabin and first class lavatory on level 2, along with level 1 maintenance bay. Marginal VFR conditions prevailed at the time, no flight plan was filed and no one appeared at the controls. The hangar was being operated under FAA PAR T .91 regulations. The day of the accident, a T hangar operating in the area reported moderate icing forming on most of its outer door surfaces. At approximately 0817 CST the following day, maintenance personnel discovered the entire passenger areas of the hangar had no cabin heat and damage to much of the domestic water system. At approximately 0923 CST the maintenance worker decided to report the accident knowing there could be consequences if he pretended not to know anything about the accident.
The wreckage was located 42 degrees north latitude, and 93 degrees west longitude at an elevation of 955 MSL. The hangar came to rest on a magnetic heading of 295 degrees 203.6 feet west from the departure end of runway 01. It was noted that this was also the exact location that a similar hangar type and color was constructed approximately 22 years ago in the same location.
PERSONNEL INFORMATION
According to FAA records, the pilots held pilot certificates with ratings for hanger single door and bi-fold door land hangars. The pilots had 73,468.4 hrs of combined hangar flying. Their most recent FAA medical records indicated residual amounts of domestic light and foreign origin toxins in their bodies.
HANGAR INFORMATION
The accident hangar was manufactured in 1986 by Professional Hangars. In 2008 N2516 underwent major renovations by its owners and was recertificated experimental. The last known maintenance was the installation of a 95%, 2 stage, 50K BTU heat generator and tank less liquid heater for passenger comfort and improved fuel efficiency. In November 2008 N2516 received a STC for the previous mentioned equipment from the local inspection authority having jurisdiction. The hangar is not required or equipped with a CVR or FDR.
METEROLOCAL INFORMATION
A weather observation taken at the time of the accident was reported as “really (unintelligible) cold!”)
WRECKAGE IMFORMATION
The debris field was spread through the entire passenger compartments. The main domestic water supply meter had 8mm and 5mm cracks along the underside main body along with cracks on the main shut off valve. The ¾ cross feed to the male waste disposal receptacle appeared to have a 6mm rupture. The level 1 maintenance compartment had approximately 8 water line ruptures. The liquid heater supply line o rings had been compromised. Level 2 lavatory water control valve on the personnel shower had catastrophic failure. Control continuity of the lavatory flush handles/linkage was confirmed and was operating at the time of the accident. The recently install heat generator had been developing heat prior to the main exhaust tube freezing solid.
PROBABLE CAUSE
The heat generator shutting down due to exhaust tube freezing. The heaters inability to maintain sufficient ambient temperature in the maintenance bay. Causal factors include: lack of insulation and low thermostat temperature settings in adverse conditions.