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Miscellaneous Luscombe Discussions

Moderator: HTB

 #12530  by HTB
 Fri Feb 01, 2019 10:28 am
Just in case you have not received or not read your LAA magazine for February, here's the recent LAA letter to owners regarding corrosion. Photos (and text) are in the PDF attachment:-

Letter to Owners
Luscombe 8 (Series) Aircraft
Head’s Up about Safety Spot Feature:
Tailplane Corrosion
30th January 2019

Dear Luscombe Owner,

We’re writing to you directly today as the owner of a Luscombe aircraft for a couple of reasons; the first is that we will be featuring a story in the February 2019 edition of Safety Spot about a recent refurbishment of a Luscombe empennage and we felt it polite to let you know about this upcoming feature. The basis for the Safety Spot essay is that during the recent refurbishment of a number of Luscombe airframes, severe corrosion was discovered within the tailplane’s internal structure. Very worryingly, on one airframe the corrosion badly affected the integrity of the brackets attaching the tailplane to the fuselage.

The second reason for writing is to ask you, as a Luscombe owner, about your experience with regard to inspections for corrosion; have you, for example inspected the internal structure of the tailplane, fin and rear fuselage on your machine recently – if so, what did you find? In addition to this direct communication to you I’ve asked Ken Craigie, our Chief Inspector, to forward this letter directly to LAA Inspectors, this will give Luscombe specialists who don’t actually own these aircraft the opportunity to pass on their knowledge. First, a brief synopsis of the basic issues.

I start the Safety Spot feature: Luscombe Silvaire owner, Peter Bentley has spent the last months with his friend, LAA Inspector, Owen Watts, renovating the empennage on his lovely machine. Peter was so shocked by what he found when he de-riveted the tailplane skins that he travelled up from his near Winchester airstrip to chat through the repair options available – essentially it was decided to, more or less, re-manufacture the tailplane. I asked Peter if he would write-up his experience for Safety Spot and he was kind enough to do this.

Peter, in his excellent write-up, discusses the need for including ‘deep’ maintenance into an aircraft’s maintenance schedule; naturally, in the LAA system, we encourage every owner to create their own, bespoke if you like, Tailored Maintenance Schedule (TMS) and we chat generally about this quite regularly in the technical output from HQ. Indeed, in the February issue of Light Aviation, Francis Donaldson, our Chief Engineer, discusses the importance of the TMS.
Of course, the Luscombe 8 aircraft in service within the LAA’s system have been around for a very long time, perhaps far longer than even Don Luscombe himself could have ever envisaged. It’s a brilliant design, though some areas are difficult to inspect, the tailplane’s interior being a good example.

It might be worth, at this point in this letter, to show you a couple of the pictures that will feature in the Safety Spot essay:

As you will be aware I expect, the Luscombe model 8 went through a number of design changes through its life, earlier tailplanes were ribbed and later types were manufactured with all the tailplane loads being carried by the spar and the skin. The picture on the right shows what was seen when the tailplane skins were lifted to carry out a ‘deep’ maintenance check – as you can see, this is an earlier (ribbed) tailplane, the ‘packing’ material is the remains of a mouse’s nest.

A mouse can get through the smallest of entrances into an otherwise seemingly inaccessible area of an airframe – the problem is, if they do decide to make the space a new home the substance of their nest will absorb and retain water (and worse) and will lead to an increased risk of corrosion.

The second picture on the immediate right shows the extreme corrosion found in the aforementioned failed attachment brackets and need little expansion.

One thing that we are being careful about is overly focussing our attention on the Luscombe airframe; we have over the years seen problems of material degradation in many types of airframe including steel tubular structures, wooden structures, composite structures and, as in this case, aluminium structures. It goes without saying that taildragger types are more prone to issues of corrosion in their empennages.

With this in our minds we’re really pushing the advantages of owners creating their own TMS which will include opportunities for deeper inspections of critical areas in their airframes; because of this recent report into tailplane corrosion in the Luscombe 8 aircraft we do feel it necessary to see how best to ensure that Luscombe aircraft operating under an LAA administered Permit to Fly remain fully airworthy.

Thank you for your attention to this letter, if you do feel that you have information that will help us with our continuing airworthiness decision making process please take the time to let us know about it. You can email, for my attention, to engineering@laa.uk.com or simply put pen to paper; pictures are always useful.

Yours sincerely,
Malcolm McBride,
Airworthiness Engineer.
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Last edited by HTB on Fri Feb 01, 2019 10:30 am, edited 1 time in total. Reason: poor spellink