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Nose Gear Strut Failure on First Take-Off
Background
On 28 May 1999 Lancair 320 G-FOPP was lined up at Cranfield Airport for its
first flight by the UK's CAA Light Aircraft Test Pilot, Bob Cole. Bob was
the original Test Pilot who had evaluated the first Lancairs in the UK and
therefore had experience on both the 235 and 320. He is ex-RAF and a
graduate of our Empire Test Pilots' School - an expert airman. Following
the usual pre-flight checks, which included a briefing for the airport's
Fire Crews on the canopy latching mechanism, fuel system and electrics, Bob
taxied to the end of the runway for take-off. I had elected NOT to carry
our fast taxy testing on the basis that I was not the person cleared by the
UK authorities (The PFA) to fly the first flight. All I had read on the
subject of fast taxiing led me to believe that it should only by carried
out if the aircraft is airworthy and the pilot is prepared to fly.
Bob released the brakes and applied full power; as the aircraft reached 65
kias he gently eased the pressure off the nose wheel in preparation to
rotate at 75 kias. As the weight was eased off the nose wheel massive
shimmy developed immediately. Within a fraction of a second the violence
of the shimmy had broken the nose gear drag link where it attached to the
oleo strut. All weight now rested on the nose gear hydraulic ram and this
allowed the gear to retract momentarily resulting in the Hartzell two blade
CS propeller striking the ground whilst under full power.
Bob Cole identified the problem extremely quickly and managed to raise the
nose with elevator, close the throttle and remain on the runway as the
speed bled away. As the nose fell back on the nose gear the weight of the
engine collapsed the nose gear by bending the hydraulic piston ramrod by
over 50o ; the aircraft struck its bottom engine cowling and scraped along
the runway for a few more yards before coming to a stop. There was no fire
or fluid leakage and Bob Cole vacated the cockpit after having closed the
main fuel cock and shutting down all electrical equipment. The Fire Crews
were on scene within a few minutes and no further damage was done to the
aircraft. The aircraft was removed from the runway by hand and recovered
to the hangar with a small hand trolley under the nose. The incident
closed the airfield for no more than ten minutes. Pre-briefing of the Fire
Crews, Air Traffic Controllers and Airfield Security all contributed to a
very efficient and careful recovery of the aircraft and I believe the lack
of post-incident damage was a direct result of my involving everyone on the
airfield with the aircraft and allowing them to appreciate not only its
detailed features (handles, fuel shut-off valve and master switches) but
also they, naturally, had an appreciation of the long-term commitment by
the builder in creating it. This meant that a great deal of care went in
to making sure it was recovered carefully. I cannot praise all involved
too much - they were VERY professional.
The Cause
>From Bob Cole's description, and subsequent viewing of a short piece of
video, it was clear that the nose gear strut had shimmied violently.
Examination of the inner faces of the nose wheel fork also showed
extensive rubber marks where the tyre had scrubbed both its edges. The
nose gear drag link had failed after what could be seen as enormous forces
being applied. The Hydraulic ram had buckled significantly. With the
aircraft's PFA Inspector (a CAA Licensed Engineer and Chief Engineer of
the FBO) I disassembled the oleo strut but could find no obvious evidence
of a failure of the internal components.
A senior representative of the manufacturer (Don Goetz) attended the
aircraft a few weeks later whilst visiting the UK. He examined the oleo
strut and declared that it should not have been shipped with the aircraft
kit in the first place as it was an example of a strut used on the Lancair
320 prototype which had failed twice in testing. He stated that all struts
of this type had been recalled through a Service Bulletin and that
apparently this related to all struts with a serial number between 1 - 50
stamped on the bottom of the foot of the strut. We examined the strut and
found a small (handwritten in ink) number on the foot - the number was
"29". Most significant of all was the information that the strut fitted to
my aircraft was manufactured by a company called "ARO TEK" of Washington
State USA. I was informed that the struts manufactured by this company had
not performed to specification and the strut manufacture had been passed to
"ESCO" in Australia.
With this information I carefully reviewed ALL Service Bulletins issued by
Lancair International which were in my possession. Whilst I could find
ones relating to the ESCO strut I have yet to find either a re-call notice
for struts 1 - 50 or any SB relating to ARO TEK struts. I have asked
Lancair International to send me a copy of the SB to which Don referred but
have yet to receive this. I have also reviewed "Lancair Mail" and "Lancair
Network News", including their full list of SB's and SDR's but cannot find
anything relating to the ARO TEK strut. All SB's, SDR's and other
references I can find refer to the ESCO strut.
Furthermore I have found a written annotation (dated 11th February 1993) in
my Builder's Manual noting a telephone conversation I had with the factory
following my receipt of SB 30-8-90 and SB 009-92 (which related to ESCO
struts) in which I asked about their relevance to my strut. My note
reminds me that the factory informed me the SB's did not apply because I
had a strut from a different manufacturer.
Aftermath
So, what lessons have I learned and can pass on to other builders or owners
of Lancair aircraft?
Well, my incident has not put me off my Lancair and I still think the
aircraft is well designed and supported by the folks in Redmond. Their
reaction has been kind, considerate and helpful in getting me replacement
parts quickly and Don's candid comments have allowed me to understand
exactly what happened to my aircraft. As any builder will know the most
disturbing thought is that there was something defective in my workmanship
or administration which caused what could have been a much more serious
incident. The nose gear strut is a sealed unit but I was still responsible
for ensuring I had complied with Service Bulletins from Lancair. This, in
my opinion, is where the main lesson can be learned and I will return to it
later.
There is little doubt in my mind that I was right to:-
a. Use a highly experienced Pilot to undertake the first flight
b. Fully brief the Fire Crews, ATC and Airfield Security
c. Not carry our fast taxy testing (had I done this the incident would
have happened to me and I doubt that I would have handled it as
professionally as Bob Cole).
d. Build my aircraft under very close scrutiny by a PFA Inspector
e. Establish a strong relationship with an FBO
f. Carry hull insurance incrementally from the day the kit was delivered.
There has been no problems whatsoever in getting the insurers to accept
liability. The current expected cost of repairs is $32,000.
g. Re-visit all Service Bulletins and Service Difficulty Reports prior to
first flight.
h. Use the Lancair pre-first flight checklist (available from Lancair).
My mistakes were:-
a. To accept the factory's telephone explanation in February 1993 that the
ESCO Service Bulletins did not relate to my nose strut. This was what I
wanted to hear but if I had asked more detailed questions about the ARO TEK
manufacturer I may have elicited a reply which would have told me I should
not have even received the strut in the first place.
b. To not have someone, like Don Goetz, from the factory do a pre-flight
inspection.
c. To not send the nose strut back for servicing after the seven year
building period. Had I done so the mistake in supplying the strut would
have been picked up by Lancair and rectified.
Lessons Learned
Seven years is a long time to dedicate to a building project and inevitably
new parts are seven years old when required to perform. I would recommend
that all builders review the components of their aircraft which may be
susceptible to ageing (e.g. oleo strut, compression donuts, gas struts
etc).
The Lancair Service Bulletin system is poor and needs urgent revision.
This is not a dig at Lancair for whom I have the greatest of respect, but
I hope that they will learn from my problem. These are my findings about
Lancair's performance as a result of this incident:-
1. The Lancair system for alerting builders to current, past or potential
problems is by no means fool proof. They issue SB's using an inconsistent
numbering system which relates to all the various models made. In my case
the Bulletins which I have received and which are relevant to my 320 are
not numbered sequentially (i.e. there are numbers missing which apply to
other Lancair models), and the actual format changes (e.g. the sequence in
1994 went as follows:- SB18-94, SB019-94 and SB024-1294). I recommend that
the SB numbering system be changed to allow SB's to be issued with a number
which is in the following consistent format:-
Model/Status of SB/SB Number/Month of Issue/Year of Issue
e.g.
320-360/M/000/08/1999
Model should cover all the various types built by Lancair and efforts
should be made to separate SB's so that they are not sent out to builders
when they are not relevant to the model being built (e.g. LIV SB's going to
235 owners).
Status of SB gives information on the importance of the SB e.g. M=
mandatory, A = advisory, C = check required etc.
SB Number an incrementing number for the model type only. This will make
it much easier for builders to know if they have not received an SB or have
gaps in their reference to previous SB's. The numbers should not be mixed
around the different models but if an SB applies to more than one model,
separate SB's should be compiled.
Month of Issue self evident but important for reference purposes.
Year of Issue self evident but must be in four number format.
2. Lancair does not provide ALL its builders with the same information and
puts too much safety related information in Lancair Mail. I suspect that
many owners may not subscribe to Lancair Mail and therefore it is a most
inappropriate vehicle in which to disseminate safety related information.
My review revealed a hotch potch of information relating to oleo strut
difficulties, servicing and general shimmy problems in Lancair Mail. There
was even conflicting information over nitrogen pressures for re-charging
the strut. Lancair must give someone the responsibility for gleaning
safety related technical information and distilling it in to either Service
Bulletins or some form of technical & safety bulletin. This does not have
to be run by Lancair themselves and is already partially covered by Lancair
Network News (LNN) and the Lancair Email List (LML). However, I believe
more careful co-ordination and dissemination of safety related information
must be done to eliminate a builder being unaware for seven years that the
nose gear strut supplied by the factory was discontinued and should have
been returned.
3. Parts picking should be more rigorously controlled to stop defective,
discontinued or poor quality parts being shipped. I suspect that my oleo
was shipped about the time the factory moved from Santa Paula to Redmond
and that my nose strut was put in by mistake. I am sure Kit Components Inc
has things under much better control today. However, my new parts for the
repair were not manufactured to the high standards I would expect so there
is probably still some work to be done.
4. The Lancair pre-first-flight check and the transitional training are
worth every penny of the good-value charge made. I gained a great deal of
confidence from my flying at Redmond and I wish I had been in the UK when
Don Goetz visited so that he could have checked over my aircraft.
5. The parts numbering system used by Lancair gives no indication
whatsoever of the modification state of the parts shipped with an aircraft.
The oleo strut which failed on my aircraft was Part No GM14. The oleo
strut shipped to me seven years later after my incident (with all its many
modifications and Service Bulletins) was still shipped under Part No GM14.
I think Lancair ought to review this policy to ensure the modification
state of a part is evident from the number being used to identify it. The
Builder's Manual does not have to specify this state but a regular listing
of modified parts, and their new suffix numbers to the original core
identification number, would help. My new strut could have been (for
example) GM14/6, to reflect that 6 modifications had been made to the
original part, including a change of manufacturer, checks of roll pins,
self centering device fitted, collar fitted to toe and any other things
done to the strut over the years.
Conclusion
I have another six months or so of work before I will be ready to try
G-FOPP in the air again. By that time I will have incorporated the new
(longer) engine mount and significantly opened up my options for improved
engine cooling. More importantly I will have a new, up-to-date, self
centering nose strut. I suppose the moral to my story is that the project
was a challenge from the beginning, almost everything about building the
Lancair has been really positive, I've made some great friends around the
world and a setback like this can result in a positive improvement to my
aircraft - with a little more work!
I hope my experiences will help other builders and that Lancair themselves
will accept my slight criticisms of them in the spirit in which they are
intended - friendly and constructive.
Happy landings to all you flyers; Happy building to all you builders;
Commiserations to us "repairmen".
Michael Fopp
Michael Fopp
Dr Michael A Fopp MA FMA FIMgt
Director
Royal Air Force Museum
Hendon
London
NW9 5LL
UK
Tel: (44) 0181 205 2266 Fax: (44) 0181 200 1751
email: michael.fopp@rafmuseum.org.uk
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LML homepage: http://www.olsusa.com/Users/Mkaye/maillist.html
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