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Beechcraft magnesium flying controls

Most early Debonair and conventional tail Bonanzas only had elevators with magnesium skin, although the earliest Debonair also had ailerons. If there is corrosion, these flying controls can be re skinned, although at some expense.

The V-tail Bonanza also uses magnesium for the ruddervators (only?), but these are less easy to repair if they suffer corrosion. As there many thousand V-tail Bonanzas still gracefully flying, and they seem to stand at a premium to their contemporary conventional tail siblings (but not the A36), what is the strategy for preserving or repairing these controls.

I’ve found a reasonably priced edition of Those incomparable Bonanzas in a second hand bookshop in Wales, and hopefully has a wealth of detail on construction and design, but it pre dates the magnesium flying control maintenance problem.

Oxford (EGTK)

RobertL18C wrote:

what is the strategy for preserving or repairing these controls.

There are about 3000 pages on this subject on Beechtalk. Currently Textron and ABS are seeking a solution but….

There is no immediate solution on the horizon, so take care of your ruddervator paint and protect the magnesium skins. They will have to last.

I renewed mines, both of them, in 2016 at a cost of 20k. I could say I am alright Jack, but that would be churlish.

This from the 19th October fromm Tom Turner, ABS..

As previously reported, they have the ability to do a very small number of skins using the metal preparation process required under Beech’s production authority. When those few skins are built we will be dependent on someone (Textron Aviation or otherwise) to certify a replacement.

As of the meeting I had with senior TxtAv a couple of weeks ago there are now five firms that have signed NDAs and received engineering data, the precursor to designing and certifying replacements. TxtAv says it with contract with a successful firm to supply parts through TxtAv, if that firms wishes such an arrangement.

SRS Aviation has obtained FAA approval to make some repairs that were previously unable to be done on ruddervators. This will eliminate some of the cases that would otherwise require ruddervator skin replacement.

Thomas P. Turner
Executive Director
ABS Air Safety Foundation

Now they will either become priceless assets, or no one will insure them. Time will tell.

Last Edited by BeechBaby at 20 Nov 20:11
Fly safe. I want this thing to land l...
EGPF Glasgow

@BeechBaby thank you, is there a reason why re skinning the elevators on a Debonair appears to be more straightforward?

When re skinning are they using aluminium?

Edit apparently there is an STC for this

Will google the ABS threads.

Last Edited by RobertL18C at 20 Nov 20:21
Oxford (EGTK)

The issue is the weight and trim set up, linked of course to the rigging. When setting the ruddervators there is a weight balance procedure noted in the Shop Manual that involves knife edge balance, and a counterweight housed in the tail section. To give you a flavour…..this from a thread in 2016 about the subject.

After you read the service manual and it specifies to use knife edges at $2000 don’t pull your hair out. They can be balanced by installing the mounting hardware and suspending the ruddervators with some safety wire wrapped around the mounting bolts and tying them to something from the celling. They must be level and then use some .041 wire hooked on the trailing edge and stretched over the top to the leading edge and hang a paper cup to fill with nuts and bolts until it balances, then weigh the paper cup. Wala! add or subtract weight until you are within the limits. The procedure is to solder some lead to the balance pad or cut some off. On several occasions I have set up a pair of step ladders and put a pipe across the top taped in place to hang the control surfaces. It works every bit as good as making a pair of knife edges to bolt to a work bench. Once I was balancing an elevator when a friend also an AI stopped in for a chat, he liked my suspension method and explained how he had used a pair of adjustable shelve supports to hang a control surface.

Now that was slightly tongue in cheek but the weight and balance weight is crucial and obviously performed by someone who knows how to do it. I am paranoid about my control surfaces and rigging pulleys. Many shops out there are clueless about this stuff.

The material used is magnesium which forms a skin around a skeletal core. Even a coat of paint can put them out of balance. Has the potential to ruin your day. The STC that you linked does not include the V tailed ruddervators, which is what all the fuss is about.

Last Edited by BeechBaby at 20 Nov 21:27
Fly safe. I want this thing to land l...
EGPF Glasgow

@BeechBaby thank you, it does look like the Bonanza community will get something organised – if you need to re skin magnesium it sounds like a very delicate bit of engineering, even before re balancing.

Is your Bonanza a V or an S? Might I ask what empty weight you have?

The version am investigating is the early Debonair because they appear to be around 1850 lbs empty and a few are now with -470N 260 hp engines, and 80 USG (74 useable) fuel tanks. Bizarrely they are on average cheaper than an equivalent 182.

Oxford (EGTK)

My Bonanza is a 1961 N model, Serial D-6795, with a Continental 6 cylinder IO-470N. 265HP. I fitted a three blade Hartzell propellor.

Max Gross Takeoff Weight: 3275 pounds
Basic Empty Weight: 2080.95 pounds
Useful Load: 1194.05 pounds
Usable Fuel Capacity: 74 US gallons/66 Imperial.
Empty CG: 79.74 inches

The earlier models have much greater useful loads and the IO470N engine is superb, with a TBO of 1500 hrs, but all run on condition if on N reg.

Some issues now developing with the IO 520/55 upgrades with cylinders not lasting very long. Lots of warranty claims. I really like the stability of the 470.

Fly safe. I want this thing to land l...
EGPF Glasgow

@BeechBaby you were ahead of the curve, the -470N is becoming power plant of choice for the pre -520 35-33 Debonair series. With a three blade propeller your V-tail must have very good take off performance, and at altitude around 165KTAS?

Last Edited by RobertL18C at 21 Nov 15:47
Oxford (EGTK)

RobertL18C wrote:

and at altitude around 165KTAS

Spot on….on a recent trip @ 8.5k, LOP, fuel burn of 11.2 Imp/Hour, I averaged a ground speed of 178kts, TAS 183kts.

I was very pleased with that performance considering I fly @65%. We did have a tailwind, but still….

RobertL18C wrote:

very good take off performance,

Yes she certainly climbs very well, again @104. I fly her by the book, like a mini airliner and she delivers every time. Consistent, speed and comfort. So after rotation I bring the engine back and I climb @ 25/25 boxed, then cruise @ 23 MP, 20.5 RPM. Seems to work and really suit this engine which remains as smooth as silk. its got 1380 hrs, top end @ 840.

Fly safe. I want this thing to land l...
EGPF Glasgow

A while ago I read about the recreation of the Bugatti Aérolithe. They described how difficult it was to shape this material. Apparently I did distort over night if not heated to the exact temperature before forming etc. So the shop which did this project should be able to build nearly any shape out of magnesium. Not sure about certification though…

I have done a lot of machining of magnesium in my workshop.

It is a rather over-rated material. For sure it is very light per volume, so everybody thinks it is amazing when they pick up a chunk of it, but it is also really weak. It works where you naturally want a large/thick structure for some reason (rigidity might be one) and then it will be a lot lighter than aluminium. But for anything thin it is useless. Higher-end laptops have their cases made from a magnesium alloy which is stiffer while still light, but whatever you do you are stuck with the corrosion issue. And if you drop a laptop, you will smash it up anyway. You can have a block of magnesium just sitting there in your house (dry and warm) and a few years later there is a 1cm deep hole of corrosion. So it has to be painted and the paint has to be really good. With a lot of the paintwork quality one sees in GA (even TBMs have had paint peeling off in big chunks off their wings, near the filler caps) the stuff wouldn’t last longer than weeks.

Hence I wonder why it was used on aircraft. It is surely not necessary. After all, you can install TKS panels on the leading edge of the horizontal stabiliser and you just re-balance the thing and it flies just the same.

Titanium is OTOH a really amazing material. Perhaps one could use it for the skin? I know you can use titanium fasteners (bolts and rivets) on control surfaces, where you have to add extra ones for some reason but overall weight has to be preserved.

Shoreham EGKA, United Kingdom
16 Posts
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