Thread: Landing Gear Information from Tom Peghiny

There has been a considerable amount of discussion recently on the CT forum regarding the strength of the landing gear on the CTsw series aircraft. In the following we will discuss what we know about the strength of the gear, the testing done and a bit of history. I am not writing this post to make any judgement of any events, just to supply our information on the strength of the CT main landing gear.

Some of the discussion has stated that “Flight Design only drop tested the plane to 21” (550mm)”. That is significantly above the ASTM (American Society of Testing and Materials) SLSA requirement. That may not seem like much out of context, but it must be understood that it is without any wing drag, lift or any forward motion, so it is only simulating the downward vector part of the total.

The original CT2K which has been in production since the year 2000 was designed for operating weights of 600 KG which is slightly higher (3 lbs) than the U.S. LSA rule limit 1320 Lbs. The original landing gear assembly of the CT2K and the early (before 2006 specification and onward) CTsw was tested in accordance with the ASTM Design and Performance standard, F2245-04.

The original specification of the landing gear had the standard gear legs, standard attachment (at the rear tunnel and bulkhead behind the seats) and the standard engine mount design. The assembly drawings from the parts manual are presented below for reference.

In 2005 the Tundra gear specification was created. This specification included larger main wheels, larger nose wheel, a reinforced central tunnel and bulkhead, stronger main gear legs, stronger attachment bracket and a stronger engine mount (which ultimately takes the nosewheel loads). In late 2005 the decision was made to make all new CTsw aircraft sold in the USA with the stronger landing gear specification, whether it was a Tundra package or not . This is one of the reasons for some weight growth in the plane since 2006.

The ASTM standard (which uses a formula identical to Part 23.725 for determining drop height) requires a limit load drop height of 320 mm (Approx.12.6”) during which no deformation can be seen. The ultimate test height drop test according to ASTM F2245-04, 5.8.1.3 is 460 mm (approx. 18”) at full weight of 600 kg. (The original CT2K specification landing gear passed this test) For the 2006 specification CTsw, Flight Design performed the drop test with a height of 550mm (approx 21.6”) successfully.

After a hard landing accident in March in Albuquerque which is referred to in the forum posting (where the welded steel part that holds the axle was broken), the National Transportation Safety Board (NTSB) specifically inspected the landing gear design, testing data, and independently tested the welded gear axle bracket of the aircraft involved. The NTSB did a metallurgical analysis and found that the material specification for the part was correct. The NTSB concluded in their report that the aircraft had a hard landing.

Flight Design also went back and reviewed the testing data and did load tests on sample parts in parallel to the investigation to make certain that the current production parts were in conformance with the test data, and no abnormality was found.

In March 2007 an independent technical audit was performed by the Light aircraft Manufacturers’ Association (LAMA) which reviews the testing and documentation of Light Sport aircraft manufacturers. LAMA uses an American engineering company to review the technical development data. During this audit the landing gear design and tests were found to be fully in line with requirements.


Main landing gear overview:

Regarding the Australian gear leg posting.

The first report of a landing gear leg failure (failure of the aluminum gear leg) was on a plane with a standard specification (pre 2006) landing gear that broke after 450 hrs of operation. It was claimed that this was fatigue due to design error. Flight Design requested that this gear leg be sent to them for analysis. They have never received the gear leg for an independent analysis. Reports Flight Design Germany received from Australia stated that the gear leg had been damaged and was used until it finally broke.

Based on this the Australian distributor has investigated planes of similar age and specification and found one leg with 500 hrs that indeed had a crack. This specific plane was known to have had hard landings. Based on this Flight Design reduced the inspection interval for cracks on the original landing gear to 300 hrs. This is the normal process - reaction to proven findings.

Another leg in Australia was claimed to have cracks after 27 hours afterwards. This leg was sent to Flight Design in Germany for inspection and was investigated independently by the German materials investigation institute (MPA) and no cracks or sign of fatigue was found.

This official, independent report of the MPA was forwarded to the customers together with the Australian Recreational Aviation Association (RAA) (The association with the delegated authority with light aircraft certification in Australia instead of the Civil Aviation Authority).

In a discussion with Oliver Reinhardt, the Technical director of Flight Design he stated: “It is the law of physics that every load bearing structure has a weak point. It is just how it has to be. No way around that there is one part that will be the first to fail in any design. Therefore, it is not surprising that, if the landing gear is loaded in the same manner, it fails in the same area. There is no reason to be surprised by this. If this were not the case it would be surprising; because this would mean that the production processes lead to varying results, which explicitly by regulations must be shown to be avoided and is not the case.”

In summary, the original specification CT gear system has been tested and passed the British B-CAR chapter S airworthiness standard, the German BFU and LTF standard and the ASTM F2245 standard. The current production specification (CTsw 2006) exceeds those requirements significantly. The testing performed by Flight Design has been independently audited by those authorities as well as the Light Aircraft Manufacturers Association and the National Transportation Safety Board.

Tom Peghiny
President Flight Design USA

Originally Posted by administrator

Another leg in Australia was claimed to have cracks after 27 hours afterwards. This leg was sent to Flight Design in Germany for inspection and was investigated independently by the German materials investigation institute (MPA) and no cracks or sign of fatigue was found.

This official, independent report of the MPA was forwarded to the customers together with the Australian Recreational Aviation Association (RAA) (The association with the delegated authority with light aircraft certification in Australia instead of the Civil Aviation Authority).

Roger
It is a pitty that you seem to be receiving some "untruths" and as I can only comment on the two paragraphs that relate to my CT I can advise that each on of them contains some kind of fabrication of the truth.
para 1. I saw the dye in a crack go about 1mm down into the wall of the bolt hole and regardless of what anyone says the LAME who I might add is very highly regarded and picked up a few more issues with my CT such as the front forks, spinner bolts etc, would not sign my aircraft out as being airworthy after 28hrs. Now, being furious with this asked to see for my own eyes and I did see it. So, what am I to do? I had an aircraft that I was not allowed to fly nor would I having seen the result. Do I wait the months to be advised that the leg was ok but then I would have been flying an aircraft that I knew had a crack in the leg.
para 2. You also say in your post "independent report of the MPA was forwarded to the customers" well I can categoricaly say that I being the customer never received any such report nor did I even hear that a report was ever done. So again people are being fed what people want to believe. What else are we being fed???

You often hear about things like this but when it happens to you and you are being told these kind of lies then it just leaves a bad taste in your mouth but the worst thing is people's lives are effected, not just the owner but their families and loved ones as well. I wonder how many times Boeing denied any liability and tried blaming pilots before they were proved wrong.

It really is a pitty that such a wonderful aircraft like the CT is involved in such antics to protect reputation and sales rather then simply working with the customers to improve things and make the CT an even better aircraft - think about it!

Sorry Roger, I must have worded it wrong as it wasn't intended at you, we have known each other to long for me to do that

As you know I have just sold my 2nd CT and was looking at getting my 3rd but I am getting scared with what is being said and who is being fed what - I don't know Tom from a grain of salt but I gather he is respected by you guys so I wonder what he is being told - I mean who would have said to him that I received a report from FD about my leg - this may answer the question.

I wonder what sort of reputation would the CT have if FD worked with its customers to make a great aircraft into an incredible aircraft???

There is so much that I could say about what has been going on and the experiences I have had with the CT over the years and I hope to get an opportunity to speak to a FD rep in a couple of weeks when my CT (the one I have just sold) finally gets the trim tab AD done (yes finally after how long has it been). For example why did I have to report to the authorities here about the chute handle inspection, why doesn't my last CT perform anywhere near as good as my first one, why does it take 6 months to get a factory fitted radio working without static, why did I have to get a brand new engine in my first CT when it was delivered (what about flight testing before it is shipped), why are the legs attached at the factory by using a hammer on the bolt to get them lined up, why are cracks appearing on the top engine cover after 100hrs, why have the welds snapped on the brackets that hold the bottom engine cover on - and boy is there so much more. Incidentally, my CT that I have just sold has the Dynon reporting the greatest force subjected to my CT was only 2.2g which can simply have come from turbulance - no hard landings

I think I will just go off now and sit in the corner like a good little boy and stay nice and quiet

It seems there are two potential problems with the gear:

1 - Failure of the welded steel part that connects axle to gear legs. This part has a lot of shear (I think it's shear) on it, and that's why it needs to be steel. Perhaps these would be better if they were a single forged part rather than welded - fewer places to fail.

2 - Cracks that propagate from holes drilled in the legs. FD has put out SB before to check for cracks around where the legs have been drilled. This will require vigilance on inspection.

Have the gear failed in any other manner, e.g., failure of the mounting points, etc? I suspect that the focus was on #2 in the past (e.g., SB issued by FD), but #1 may still need to be addressed by FD.

Doug

Roger,

I find Tom's post disturbing as it portrays second hand information as factual, when indeed it represents a mix of some truth, half truths and errors. Being one of the parties involved first hand I have so much more to say on this subject but feel obliged to withhold to avoid the appearance of defaming the character of others, which would not be in the interest of this forum.

With respect to voicing my assessments of the CT design and issues relating to that I reserve the right to have my say. If we all choose to sit by quietly saying nothing so as not to upset FD we risk others being hurt or killed. Come on Flight Design, get ACTIVE about consulting your many product users, listen to them, give fair consideration to their experiences and needs. Sure, it might cost you some of your profit margin but your product and more importantly your integrity will benefit greatly. Without quality customer service a business will die ... probably not all that apparent in US but it is here.

Paul

Originally Posted by Doug

Has the gear failed in any other manner, e.g., failure of the mounting points, etc? I suspect that the focus was on #2 in the past (e.g., SB issued by FD), but #1 may still need to be addressed by FD.

Doug

Yes Doug, other types of failure/wear are out there. I have experienced three (and I've heard of one other) that have not been covered yet.

But I wonder if my input will be regarded with any credibility or just passed off as the whinging of a disappointed owner (disappointed by lack of support but still happy with the CT experience).

Paul

Paul

You bought my used aircraft. After you had flown over 200 (230-250?)hrs, learnt to fly in the plane and done hundreds of landings, there was a landing gear failure... was the landing gear inspected as required in the 100 hourly inspections? there were obviously 2 such inspections during this time.

The first we (FD, Leo or Myself) knew of your incident was 5 days after the event when we heard about it from another CT owner. I immediately contacted you, it was a Sunday afternoon. The first thing I asked was if everyone was OK and then about the state of the plane.
I put you in contact with our composite man who provided a quote to repair the plane. This happened within about the first month.
WE (FD) offered to replace your landing gear so that it could be analysed and the cause of the failure determined. You refused to release your broken gear to FD. Your decision to repair the plane using your own resources was the reason the repairs took hundreds of days. It was more than 6 months after the incident before you were "ready to order" any spares and a little later you emailed me saying your repairman would be ready to start the composite repairs sometime in December, 13 months after the event. I can't say there weren't a few problems getting your spares, but .. you got them, you were not invoiced for all of them and you were not charged full price as we were sympathetic to the fact your plane was not insured.

At some stage, CASA was asked to make a call on the adequacy of the landing gear and it was determined it was adequate for its purpose .. landing gear... this is simply a confirmation of the ASTM, BFU and LTF standards to which the plane conforms. To this day, no representative of FD has seen been able to inspect your failed leg as you kept them "pending developments over the next few weeks" .. an admirable approach to the safety of the fellow aviators you bemoan.

It would have been much easier to insure the plane in the first place.

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Ian

Your 28 hour leg. I was informed by you .. "could be a problem, he (LAME) is not sure .." The LAME called it correctly and further analysis was required.
FD replaced your legs as soon as it was learned there was a problem. This was done at no cost to you in parts and labour.
I packed your legs and sent them to FD in Germeny. When they arrived, a Metalurgist present to ensure no funny stuff. They were analysed at the Materialsprufungsanstalt at Stuttgart University. There was no crack. The report was forwarded to the RAA in March 2006.
I did not forward it to you as it is in German but I phoned you and discussed the results. We also talked in depth over the condition of your plane while it was available for hire, on more that one occasion (remember spinner, nose wheel wear .. chips in the paint in places we thought not possibe), probably in one of your Sunday night after 10pm calls, or maybee the Saturday morning before 7 am ones.

Your landing gear was replaced, at our cost, the suspicious "crack" was analysed at a world class lab and no defect was found.

Everybody has had a hard landing, I have had more, some would say lots more. You seem to forget I was in your latest plane and experienced a landing where the dorsal fin and the ground contacted, with one wing significantly higher than the other. That was not your best landing .. it happens.

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For the other readers on the forum comments on ..

About Us

Leo and I bought CTs before ever considering importing the plane into Australia. I payed my deposit and then held delivery until the certification was completed (with the understanding that if we couldn't get it certified I would get my money back). There was a legislative change, but it took nearly 2 years to receive permission to fly the plane. We approached FD to import the CT simply because it had taken so much effort to get it certified. The CT was the first foreign built ultralight certified in Australia.

We love the Ct and think is the best all round plane in its class .. bar none. Unfortunately Leo and I (a Senior Airline Captain with nearly 45 years of flying and an automotive design engineer with 25 years international design), don't get to fly our planes as much as you guys, but as often as we can we're up there.

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Service Down Under

The biggest problem we have is supporting a very small customer base (18 planes) in a country the same size as the USA .. For example, from Melbourne, the furtherest customer is over 20 (CT)hrs flying away on the western side of the country and we have one plane 16 (CT)hrs flying away on the eastern side of the country. One plane took 15 (CT)hrs flying to deliver. The solution we have is as simple as we can make it .. mobile phones. Our phones are turned on "all" the time. We are available "all" the time and take plane calls even overseas on other business. Planes are imported to 3 cities depending on final delivered location and we have expert composite repair people and LAMEs at these locations. Most planes are maintained by the owners, but there are hundreds of LAMEs around the country; all with GA maintenance certficates. We often get calls from LAMEs asking technical questions, if we are unable to provide adequate information, FD has always come through, always. This has proven to be very effective method of solving the vast majority of issues. Lets not pretend there aren't problems, there are occasionally. The number of unhappy customers is limited .. to just a couple, but even with them we get it right occasionally


Paul Nossiter .. "Once again, thanks Shaun. That was pretty quick work getting Matthias's endorsement"

Paul Nossiter .. "Something I have noticed about Flightdesign and both Shaun and Leo ... your willingness to help is impressive, and certainly appreciated."


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Comments on Training

I don't believe there is a problem with the strength of the landing gear. We have been flying the CTs for over 6 years now and it has been our experience that the CT will test your airmanship. As with any high performance machine, it demands the greatest amount of respect you can afford it. If there are shorcomings in your training, it will show somewhere. (With the similarity in incidences in the USA, it almost looks as thought there are only a few instructors over there who do all the training??)


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Comments on Landing?

To land the CT you need to slow it down. When it is flying slowly, it feels like it is wallowing, pehaps it is, but the controlls remain responsive all the way down (height and speed) Try this .. go for a fly, get some height, fly at 55 knots for 1/2 hour (with landing flaps set), now do it by trimming the plane to fly "hands off", now do a 2 mile approach ..... remember it's a low inertia plane, if you bounce, don't push the stick forward and if you're unsure or uncomfortable get more training, and more and more until you're have mastered what needs to be mastered..


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Remember for the whole of your life, every piece of machinery you ever use, from a can opener to a Jumbo must be operated within its design parameters to achieve optimum performance .. The CT is no exception

If any Ct-ers find their way down under, please feel free to contact us. We are only too happy to talk planes. We would like to make the trek to Fun&Sun (although it is a very long way!) and experience American Aviation .. you guys seem to do everything on a scale we can't come to terms with.

Shaun and Leo

I think the final nail has just been driven into the coffin of the CT here in Australia.

Let the readers judge . If you feel my integrity is lacking say so. If not I could do with some encouragement right now to remain as part of this community without fear of having being shamed.

Paul