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If you don't want to fly around thunderstorms in Florida
in the summer months, don't fly. But I got more than I bargained for in
my most recent flight from Lancaster, Pennsylvania to home base in Boca
Raton Florida.
Friday, June 13, 1997
The
usual clusters of storms over the Southern Florida peninsula were evident
both on the radar picture I got with my weather briefing, my eyes in the
cockpit and on the color radar in my Aerostar 601P, N6069N. There was one
big storm over Daytona Beach which was easily circumnavigated by going
about 5 miles west of the OMN VOR and then turning to intercept V3 southbound.
Ahead looked more ominous. There was a line of storms starting about Melbourne,
Florida that looked, at least to the eyes, solid. ATC suggested heading
southeast where "everyone else" was going through. After consulting the
radar and the WX-8 stormscope I headed about 120 degrees, about 30 degrees
east of the normal V3 routing.
The
cells stood out very well on the radar as large red blobs; there was on
over land near Melbourne and one well out to sea, with very little precipitation
in between. The cells were separated by about 50 miles, and it looked like
a good plan. I began my descent from FL220 to 16000 feet about opposite
Melbourne and soon entered the clouds. There were one or two small patches
of level 1 (light) precipitation showing on the radar and there was some
moderate turbulence as I flew through them.
Each of these little areas
was about 2 miles wide with light rain on the windshield. Somewhere in
the continued descent I saw a lightning bolt off the left wing, at the
same time I heard a "whoooosh" – nothing else. The avionics never wavered,
no circuit breakers popped, in short nothing happened. I estimated the
lightning bolt to be about 1 mile away. I was more occupied with flying
the airplane in occasional moderate turbulence and studying the radar than
thinking about a lightning bolt that I thought was more than a mile away.
About this time ATC suggested a turn back toward the airway. I declined based on the radar and flew another 10 miles before turning back towards the coast. After the turn, the clouds broke up and it was VFR the rest of the way to Boca.
On
the ground I noticed that one corner of the left propeller looked chipped.
A close inspection revealed a jagged break of about ¼ inch and the
aluminum looked like it had melted where the piece broke off. 
There was
a slight discoloring of the paint and I immediately thought that it had
been hit by lightning. I walked around the left wing and saw the three
pencil sized holes in the trailing edge of the flap. There was a slight
discoloration in the paint here as well. Continuing around the tail appeared
to be undamaged, nothing on the flap on the right wing….then I saw the
large, fist sized burn on the top of the right wing outer panel near the
trailing edge. The screw in that area had been melted and a small piece
of melted aluminum was also visible near the trailing edge.
The airplane had flown perfectly, with no hint of any problems all the way to BCT. The avionics appear to be undamaged. The burn mark on the right wing was about 12 inches from the fuel tank in that wing which certainly makes me nervous and I guess makes me lucky- if anyone hit by lightning can be called lucky.
Monday June 16, 1997
What Now?
There
are several service bulletins relating to what you have to do to engines,
propellers and the airframe in the event of a lightning strike. Some, but
not all of these are to protect the manufacturers against any liability
from subsequent failures.
So far this is clear:
-
The left flap skin has to be repaired. -
The right wing outer panel has to be inspected and repaired.
-
The left prop hub has to be taken apart and inspected.
-
The left prop blade that was struck may have to be replaced.
-
The wing structure must be thoroughly borescoped for internal damage caused by arcing.
-
The left engine must be torn down, inspected and demagnetized.
-
All the avionics must be checked for proper operation.
Tuesday June 17, 1997
More damage was found on the clear plastic cover to the wingtip strobe and recognition light. One screw was burned and the washers all showed some heat damage. There was a small burn mark inside the plastic lens as well. No other external damage has been found.
Palm Beach Propeller shop examined the left engine with a gaussmeter
and found that it has a significant amount of magnetism. The right engine
showed none and this adds to the belief that it escaped any consequences
of the strike.
Lycoming issued a service bulletin for lightning strikes on June 30,
1976. Here is the text of that bulletin:
Lycoming Service Bulletin Number 401The new flap skin is scheduled to arrive tomorrow.Date: June 30, 1976
Subject: Recommendations for aircraft struck by Lightning
Models affected: All aircraft powered by Avco Lycoming engines
Time of compliance: Anytime aircraft is struck by lightning
Damage to an aircraft, which has been struck by lightning, is usually apparent and often confined to a specific area of the structure. In such instances where the engine and its accessories, controls, fuel or exhaust systems are involved it is necessary to evaluate and repair the damage before the aircraft is flown again.
Although the path of the lightning may appear to have been around the external housings of the engine components, it is nevertheless impossible to asses the internal damage that might have occurred by heat during the lightning discharge. Therefor, in the event the engine has been damaged by lightning, disassemble and inspect the component parts. Heat generated by the arcing effect of the electrical discharge can cause irreparable damage to the hardened surfaces of ball bearings, crankshaft bearing surfaces, camshaft lobes, gear teeth and other parts that are surface hardened; these should not be reused if discoloration, cracks or other indication of damage by lightning is evident.
I'll continue to update this as it happens.