Lightning, Corona, and Icing, oh my!

I was rummaging through the Cozy archives and found this very interesting newsletter from 1995. Original was 1987. Read on, wow!...

 

 

 

The following three letters are concerning a lightning strike on a

Long-EZ flown by Dick Kreidel. We certainly thank Dick for taking the

time to write the account which Burt sent to Andy Plummer for his

comments. Mr. Plummer is one of this countries leading authorities on

lightning strikes and his letter is, also, reproduced here for all of us

to read and inwardly digest. Pay attention, guys, our EZs are not

indestructible, although many of us fly them as though they were.

 

"I deliberated for a long time whether to publish this account of poor

judgement and foolish mistakes. When I read it now, on the ground,

three months later, the faulty reasoning is easy to see. But I assure

you, that the decisions and events on May 23rd were made to the best of

my ability and skills. My hope is that someone will benefit from my

errors. It is a fine line between being around to tell a story and not

being around.

 

This account was originally sent to RAF for their comments. Burt passed

it on to Andy Plummer of Lightning Technologies who is reputed to be the

foremost lightning expert. Mr.Plummer's comments follows my tale......

 

I departed New Orleans Lakefront Airport IFR to El Paso at approximately

9:30 a.m. local on Sunday, May 23rd. I had received a thorough weather

briefing from Flight Service only 20 minutes earlier and they indicated

that westbound I shouldn't have much problems; rain showers and multiple

cloud layers with tops at 14,000' to 16,000' MSL with a thin cirrus

layer at 25,000'. Live Radar and FSS painted a line of thunderstorms

about 20 miles south but it probably wouldn't arrive at Lakefront for at

least an hour. I was cleared to 16,000' and had gone through multiple

layers of cloud and picked up some light clear ice after a climb through

12,000'. I requested from ATC to hold at 14,000' for a while since I

was between layers and the next ceiling didn't look as thin as

advertised. The OAT at 14,000' was +1 degree C. I flew through some

heavy rain and more ice accumulated on the plane, especially the canard,

elevators and vortilons. The wing did not appear to have much ice on it

and I could not see any on the winglets or the intersection between the

wing and winglets. Indicated airspeed at 2400 RPM was 122 KIAS. The

ice on the canard covered about 20-25 percent of the chord with some

"streamers" that went back to perhaps to 50 percent chord line. Ice

formed below the trailing edge of the elevator about 1/8" thick with a

uniform spanwise distribution. The ice on the canard was definitely

clear ice but what was below the trailing edge of the elevator looked

more like mixed or rime ice. The elevator position was about 5/16"-3/8"

T.E. down. The airplane was very controllable with good elevator

responsiveness. I could have easily climbed if I had wanted to so I was

not overly concerned.

 

ATC was giving me radar vectors to stay clear of any CB's but indicated

that contrary to my preflight weather briefing, the "weather west of New

Orleans is really wicked with the big boys having trouble going

through!" Center advised that the only way they felt would be O.K.

would be to deviate approximately 60 nm due North - obviously I followed

their recommendation. After a few minutes I was again in cloud and it

became increasingly difficult to hear radio transmissions - static was

all that came through the headset.

 

I started receiving small electrical shocks from the roll trim lever

through my jeans and shocks from the microphone to my lips. I became

aware of the transparent blue glow that was on the nose and canard. I

say blue but somehow it seemed blue with a pink tinge. The color was

similar to the bright blue from a gas welders flame. This halo was

about one chord width above the canard and seemed to "move" - it is very

difficult to describe in words. I was now getting shocked through the

speed brake handle and from the rudder pedals to my ankles (my feet were

in the relaxed position forward of the pedals). The B&D tachometer was

bouncing erratically from 500 RPM to full scale and both Nav CDI

displays were swinging from stop to stop. The electric engine

instruments were also useless - I didn't notice what the wet compass was

doing. Here I was: IFR conditions, icing, no communication or

navigation, thunderstorms and weird light. So far the ride was smooth

with no rain or hail in the cloud - the cloud was not a dark, heavy one.

The blue (pink) glow increased in intensity and its movement was more

rapid. I am not sure but I believe that the blue glow was now inside

the cockpit between my face and the instrument panel, but I could still

easily read the gages; it was right out of the Twilight Zone.

 

I saw a bright flash way ahead of me that seemed to go from left to

right that really lit up the cloud I was in; I assumed that it was cloud

to cloud lightning and that I was definitely in deep grease! The com

was still all static and calls to center were unanswered (or perhaps

unheard). I was so scared that I was sure that this would be the way it

would all end and Kay (my wife) would really be pissed! I smelled a

thick sweet odor, got one good shock from the microphone and then there

was a tremendous flash of light and an incredibly loud "crack" - I felt

it in my bones and chest as opposed to hearing it.

 

I had been looking out at the right wing trying to figure out why the

blue halo was not on the wings, only the canard, when the flash

occurred. I was temporarily blinded so I removed my hand from the stick

hoping I wouldn't enter a spiral dive. When I could see again (10-15

seconds), to my amazement 1) I was still alive and 2) the plane was

still level at 14,000' on my last assigned heading of 060 degrees. The

blue halo was gone and I heard a transmission on the com for a Delta

jet. I called center to see if my radio was blown and they immediately

answered my call! Apparently they had been trying to reach me to give

me a new vector and immediately turned me to 330 degrees. The airplane

was again between layers and the visibility was good, I could even see

patches below. Everything appeared to be working O.K. but the plane

still had a lot of ice on it and I didn't think I was in any mental

state to fly an approach. The airspeed now read less the 50 knots so I

knew that the pitot tube had iced over. The weather seemed to be

improving rapidly with a broken layer above and below with some

beautiful blue sky far in the distance. Since the plane would easily

climb with full power and the remaining aft stick I saw no reason to

descend and kill myself making a lousy IFR approach after all of this!

I then saw several dark patches on the wing and winglet leading edges

that upon later inspection were areas where only the glass skin

remained. In about 20 minutes all of the ice melted and the elevator

position returned to 1/16" T.E. up and the airspeed increased to 140

KIAS at the same power setting of 2400 RPM. The flight continued

normally in IFR and I landed at El Paso International four hours later.

 

So what is there to learn from this unwanted experience? Probably

several things. First, that the invincibility I felt in B888EZ

contributed to my cavalier attitude in flying in bad weather - this

certainly was not the "California IFR" that I was used to. After nearly

1100 hours of flying in a plastic cocoon, I had developed a false sense

of immortality - after all, the EZ had gotten me through some tough

situations before. Also, I learned to never, ever trust ATC and/or FSS

- the pilot must make his own decisions and evaluations on when to

commence or terminate a flight.

 

Another significant revelation is that although the Long-EZ is a great

plane and can leap tall buildings with a single bound, it is not suited

for hard IFR flights with embedded thunderstorms. I consider myself

extremely lucky to have survived this flight - my skill and judgment (or

more correctly - lack of both) hopefully will serve me better in the

future. Dick Kreidel"

 

**From CP44-3**

LIGHTNING TECHNOLOGIES, INC.,

10 Downing Parkway,

Pittsfield, Massachusetts 01201

(413)499-2135

 

22 July 1987

 

Subject: Long-EZ Lightning Strike

 

Reference: Your Letter of 3 June 1987, Same Subject, with

Dick Kriedel's Letter Attached

 

Burt Rutan

Scaled Composites, Inc.

Hangar 78,

Mojave Airport

Mojave, CA 93501

 

Dear Burt:

 

I have studied the interesting account of a lightning strike to

a Long-EZ by Pilot Dick Kreidel, accompanying your letter of 3 June, and

have the following comments:

 

1. After beginning the deviation North, the aircraft entered an

electrically charged region, as indicated by the static in the

communications system, "small electrical shocks" and "blue glow"

(corona) on aircraft extremities. The electric shocks were due to

electric field penetration of the non-conductive fiberglass airframe.

The erratic behavior of the instruments was also due to electric field

interaction with the interconnecting wiring. It is very likely the the

corona was indeed occurring inside the cockpit as Mr. Kreidel

suspected.

 

2. The synoptic weather conditions reported by the pilot are very

characteristic of those reported by other operators when lightning

strikes have occurred (~14,000 ft; icing, precipitation, within a cloud,

OAT +/- 5 degrees of freezing). Apparently the aircraft was near

embedded thunderstorm cells, though lightning strikes have been known to

originate in "layered" clouds as well as CB clouds.

 

3. The "flash of light" and "loud crack" indicate a lightning strike,

although evidently one of mild intensity as indicated by the

comparatively minor effects on the aircraft. At 14,000 ft. it is

likely that the aircraft encountered a branch of a flash, rather than

the main channel of a cloud-to-earth flash; as illustrated in the

following sketch. **SKETCH OMITTED**

 

4. The electric currents in a branch (of which there are a lot in a

typical flash structure) are usually much less than that in the main

channel. Even so, the flash and noise can be frightening if experienced

close at hand.

 

5. Apparently the lightning current entered one wing tip (take your

pick) and exited from the other, being conducted by internal metal

conductors between. The amount of damage to the fiberglass and foam

structures indicates a very mild strike - perhaps 5 kiloamperes or less

(Part 23 rules require an airframe to tolerate 200 kiloamperes).

 

Comments

 

1. Pilot Kreidel was lucky! A more severe strike may well have caused

major structural damage and lethal voltage difference among metal

objects in the cockpit (column, pedals, headphones, etc.) as well as

severe damage to internal electrical conductors such as control cables,

hinges, bearings, rods, electrical wiring, etc. These voltages and

currents can be far in excess of fatal levels. Electric fields and

lightning strikes themselves will directly penetrate unprotected

fiberglass structures, attracted by metal objects within - not matter

how small.

 

2. This is another example of the fact that ATC cannot be relied upon

to vector an aircraft safely around- and clear of - hazardous

thunderstorms. Controllers are not provided with sufficient (and

timely) information for this purpose. Even though avoiding areas of

heavy precipitation the aircraft ran into an electrically active region.

 

3. This incident is not a good example of what would occur to a Long-EZ

in a lightning strike. A "full threat" stroke would likely have ripped

a hole a foot in diameter through the composite and vaporized small

diameter control cables and interconnecting wiring. The accompanying

shock waves would have caused extensive internal damage, delamination,

etc. I doubt very much whether the aircraft or pilot could have

survived such a strike.

 

Recommendation

 

1. Continue to warn pilots of this class of aircraft to stay VFR and

avoid "weather" clouds, precipitation and icing within 5 degrees of the

freezing level should especially be avoided.

 

2. This Long-EZ should be thoroughly inspected to be sure that there

has not been damage to any internal metal parts. All internal parts

should be inspected. It is quite probable, for example, that this

strike burned some strands of control cables, electrical wires, etc.

 

Thank you for sharing this interesting account with me. Please

give me a call if you have any further questions.

 

Yours truly,

J.A. Plumer, President

Lightning Technologies, Inc.