While in flight, the Champion 7GCB’s rudder cable separated. The pilot was able to return to the airport in Pearsall, Texas, and align the airplane to land.
During the landing flare, the plane began to drift and the pilot was not able to correct the drift. He initiated a go-around, however the airplane then entered an aerodynamic stall and subsequently hit the ground.
Examination of the rudder cable separation area found localized melting, darkening, and oxidation consistent with electrical arcing. The elongation and oxidation of the overstressed wires was consistent with separation at high temperature.
According to the pilot, the passenger had gotten his foot caught in the rudder cable. The pilot believed that the rudder cable came in contact with the battery at that time; the battery box did not have a cover, and the positive terminal of the battery was unguarded. The contact would have resulted in the electrical arcing and the subsequent cable separation.
The NTSB determined the probable cause as the failure of the rudder cable due to electrical arcing damage from contact with an unguarded battery and the pilot’s subsequent loss of control during the go-around.
NTSB Identification: CEN13LA518
This August 2013 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
That series of aircraft have a history of battery arching problems, due in part to the lack of inspection, (behind baggage sack) and redesign of battery hold down methods and battery boxes. Some of which are soft plastic with a clear plexiglass top covers.
However, the battery terminals should always be protected from arching into cables or structure. That is the reason for the rubber boots.
The photo of the battery box (in place in the back of the Champ) from the Docket (go to: http://dms.ntsb.gov/pubdms/search/hitlist.cfm?docketID=55362&CFID=132515&CFTOKEN=814e5c2878365d0f-AB441FF2-CBAA-D365-0C69E8B2C380C5B5) and take a look at photo4 shows a multitude of issues:
The battery box was not secured in the aft compartment; the box didn’t have a cover; the terminals were exposed from the battery post to the beginning of the insulation; the insulation on the negative terminal was worn through from contact with the rudder cable (it was not a ‘new’ problem caused by a foot getting stuck in the pedals…); the rudder cables were just a couple of inches above the exposed terminals of the battery; the rudder cable was aligned with the two terminals – not much clearance at all!
The aircraft wasn’t airworthy, let alone ‘safe to fly’.
The pilot and pax were very fortunate it turned out without serious injury to either. With the arcing and flying molten metal an in flight fire was a possible outcome.
The battery box cover is on the floor at the bottom left of the photo. So, again, why would it be flown like this? The good news as you said is they got out of it okay, other good news is that with a stated 17,000+ hrs of flight time the insurance companies would love this guy as very low risk.
Obviously this was a “chain” of links leading to a mishap anyone of which had it been removed would have prevented the mishap. Most notable among the links was the proximity of a primary flight control cable passing in proximity to an unprotected battery terminal or the apparent ease with which a passenger could become entangled with said cable.
What happen to pilot not inspecting plane equipment