Aircraft inspection

JT442

Thank you. Your modesty becomes you. Please be free to use the content of my last contribution as a teaching aid. Alternatively, if you think that it would prove useful, I would be pleased to talk to your students on the subject of “Look, touch, feel” in aircraft design.

John Green

Yes I am an aeronautical engineer, with a mere 15 years eperience on aircraft ranging from the Bristol 188 (in preservation) through to Flex wing Microlights, Piper products, military jets and rotary, to A310 and Boeing 747s. I now teach aircraft engineering, particularly structures and systems.

I bow to your evidently superior knowledge as a private pilot. :rolleyes:

JT442.

Thank you for that. I’m very pleased that my attitude disturbs you. It will perhaps serve to separate you from that rather comfortable complacency that is so apparent in your contribution.

Take a tip from me. Take nothing for granted. Take nothing for granted that appears to be endorsed or supported by the professional. Make your own enquiries. Give your native common sense free rein. Ask yourself questions. Ask if it is rational. Ask if it appears to make sense. Ask if there could be some hidden agenda. Trust, but only conditionally. Always check, check, and check again.

By all means trust your professional, that is what they are there for and why they get paid. But do your own checks. When a check is done outside of one’s professional capacity, one does it from the purest of motives – not for financial reward.

I know from personal experience based upon the professional examination of both certified and uncertified aircraft that one CANNOT rely on the professional discovery and disclosure of faults. If they can be overlooked, they will be. Check and check again.

You write that what I’m complaining about has just become apparent. That tells me that you haven’t properly read my comments. I’m not complaining, but merely highlighting what I see from many years experience, is a rather disturbing anomaly; the anomaly of not being able to properly access and examine the inside of an aircraft. I believe that this anomaly needs a solution provided by accountants mindful of legal obligations as yet non existent. Accountants run businesses not designers.

It is ridiculous for you to write that one small hole in the fuselage will provide visual access to the whole – it doesn’t – it can’t – it’s impossible. Yes, I do worry that the main spar might drop off, if I can’t see it. I admit that it is unlikely but even more unlikely if I can see it and inspect it preferably by touch and feel.

I don’t know whether or not you are an aeronautical engineer but, if you are I shouldn’t have to tell you that it is possible to design an aeroplane that is full of holes and a whole lot stronger than a wet tea bag – they exist in plenty, they are called microlites (sic).

I do not share your optimism regarding manufacturers and designers particularly when they are designing and manufacturing with regard to the profit motive and their shareholders. Defence procurement particularly is stuffed full of examples of the “that’ll do” mentality. Resulting in artefacts that are deficient for their design purpose and rely on human improvisation to redress their faults.

I conclude by stating that your unworthy innuendo regarding my comments on aircraft insurance are just tripe. My comments were directed at the CAA and their clumsy attempts to monitor aircraft insurance uptake and continuity.

If you are sincere in your wish to have a long or short conversation with my Inspector please confirm such and it will be arranged.

John Green

GA aircraft only. Ok, so finally I can see what you’re complaining about. Small aircraft are designed with few access hatches simply because they are so small. One small hole in the fuselage allows visual access to the whole of the structure – there is no need to have more. I know you want to inspect everything on a pre-flight, but provided you fly your aeroplane within its design limits and store it in a suitable manner when not flying it, faults WILL be picked up on the routine inspection schedule – that is why it exists. As part of that schedule, the usually inaccessible parts of the airframe will be accessed. Corrosion does not suddenly occur, but will develop over time – part of a fail safe and damage tolerant design. Relax, do your checks as per the manual, and allow the engineers to do their job when the manual calls for more detailed checks. Don’t worry about the main spar dropping off if you can’t see it – every aircraft and the material it is made from has been subjected to the most rigorous tests to ensure that it will perform for a certain length of time within a certain flight envelope. The dangers only exist when the design limits are exceeded or the life of the component is extended without authorisation.

I would rather have a structurally sound aircraft which is re-skinned every five years than an aeroplane which was full of holes and about as stong as a wet tea bag.

Your scepticisim of the manufacture, design and engineering industry is disturbing, particularly when your previous threads mention the possibility of flying without insurance… I sincerely hope that your personal standards would prevent you from doing anything dangerous. I would love to have a long conversation with your designated inspector….

JT442

Thanks for that. I’m almost re-assured. Almost. I’m not likely to fly a Wessex (don’t know how). 737 ? Very exotic and a fuel burn that my pittance of an income could hardly match. Currie Wot ? The one I looked at – one of very few in Britain, so I’m told – had no inspection holes that I could see. I’m not writing that it didn’t have any; I couldn’t see any.

My comments regarding this subject relate entirely to GA a/c of my experience.

John Green

http://i.dailymail.co.uk/i/pix/2011/06/14/article-2003052-0C8A809400000578-504_964x482.jpg

http://www.decodedstuff.com/wp-content/uploads/2010/11/see-through-planes.jpeg

http://www.craftsmanshipmuseum.com/images/ParkAC1.JPG

The Westland Wessex has 40 access panels. The Cub has half a dozen. The 737 has a couple of hundred. In other words, the designers are building their aircraft (including the Currie Wot with the correct number of access ports.

Yesterday, I was in a hangar gazing fondly at two Piper Cubs and even more fondly at a Currie Wot – all, failrly ancient designs if I know the meaning of the term.

As a matter of interest, I found five inspection apertures on each Cub but none on the Wot. Both Cubs had two large approx. 3′ x 2′ hatches giving access to each wing fuel tank. The Cub hatches looked as if they had been ‘designed in’ during the design stage.

I’m thinking of offering a prize of a type that links to the subject in question to be awarded to the first person finding and describing a viable and current flying machine with the most number of usable and sensibly placed inspection hatches.

John Green

Tornado 64

I don’t think that the manufacturers have “teams of engineers looking into whether it is worth including inspection hatches”.

I think that they probably have teams of accountants looking into the financial merits of such and concluding that because of the extra costs associated with the design implications and the lack of official minimum standards, they aren’t strictly necessary or indeed, as they should be, a legal obligation.

This situation will not change until someone, regretably, has an accident and it can be proven, perhaps in Court, that the accident was due to a manufacturers negligence in providing satisfactory inspection hatches.

John Green

the way i’d look at it is that the more you interfere with an engineered structure the more streangth and integrity you take away from it !!

i liken it to cabriolet versions of saloon cars the roof is taken away wich removes most of the engineered structures rigidity making it necessary to add streangthening in key stress areas all over the remaining body shell

but the original streangth can never be recovered fully

my guess is that the aircraft companies have teams of engineers much more qualified than you or i that did look into wether inspection panels were worth including for the estimated end of life period for the aircraft and it was deemed not necesssary !!

Tony T

Credit to you. Bags of info, although for my personal taste too much on fuel tanks. I was rather aiming for the inclusion at the design stage of an inspection hatch permitting access to check condition and clean the tanks – once in a while not every time I take wing.

JT 442.

You’re right. Too many holes – not good. The right number of inspection hatches correctly sited – very good engineering practise and very necessary.

If the job is done correctly with proper planning and thought applied at the design stage, recourse to the LAA modification system is un-neccesary. I can’t understand the ongoing debate. It is all about designing the machine properly in the first place so as to permit easy access and maintenance. Simple.

John Green

Tony, your CD is still in use almost every day (although we now have it spread across a couple of hard drives too), so another thank you! …. and it was the full set 😀 We have all the documents for the Aztec, including parts manual and pilots notes so I think we’re pretty much sorted for that one now.. (If you have a Jetstream 200 manual knocking around I will swap you a kidney for it…)

Good picture of the tanks too.

Oddly enough, there is an article on modifications in the latest LAA magazine, and it says pretty much what has been covered here – too many holes are bad, and if there is an absolute need to access something, submit a MOD to the LAA (or CAA/design authority) for bigger stuff…. but bearing in mind that any new hole must be stronger than the original skin, and therefore heavier….

Do you want the engines one? includes ohaul.
Pics are off a breakers site 🙂

Tony, your CD is still in use almost every day (although we now have it spread across a couple of hard drives too), so another thank you! …. and it was the full set 😀 We have all the documents for the Aztec, including parts manual and pilots notes so I think we’re pretty much sorted for that one now.. (If you have a Jetstream 200 manual knocking around I will swap you a kidney for it…)

Good picture of the tanks too.

Oddly enough, there is an article on modifications in the latest LAA magazine, and it says pretty much what has been covered here – too many holes are bad, and if there is an absolute need to access something, submit a MOD to the LAA (or CAA/design authority) for bigger stuff…. but bearing in mind that any new hole must be stronger than the original skin, and therefore heavier….

Do you want the engines one? includes ohaul.

Tony, your CD is still in use almost every day (although we now have it spread across a couple of hard drives too), so another thank you! …. and it was the full set 😀 We have all the documents for the Aztec, including parts manual and pilots notes so I think we’re pretty much sorted for that one now.. (If you have a Jetstream 200 manual knocking around I will swap you a kidney for it…)

Good picture of the tanks too.

Oddly enough, there is an article on modifications in the latest LAA magazine, and it says pretty much what has been covered here – too many holes are bad, and if there is an absolute need to access something, submit a MOD to the LAA (or CAA/design authority) for bigger stuff…. but bearing in mind that any new hole must be stronger than the original skin, and therefore heavier….

Progress 1: (21:37) The Piper range of light aircraft seem to have integral tanks (structural), so you can’t remove the tanks without the wing falling apart unless you trestle and rig the wing. You can see three of the six sides just by looking from the outside, and you can get a mirror into the tank by the filler cap. Any more holes to see the inside, and you’ll struggle to keep fuel in… removal of the tank is possible for detailed inspection / pressure testing, etc, but not pre-flight. The only aircraft I can think of which has panels such as what you want, are the Lancaster and Shackleton where you have 10ft square panels to allow the removal of the rigid tanks. Having removed said tanks, I don’t recommend doing it on a regular basis. (Why would you want to?) There is no facility to look at the top of the tank when it is fitted, and again unless it’s broke, I’m not interested in it.

JT442

Piper Seneca, Warriors etc etc have a structural tank that is screwed along the spar and down the ribs, it is a metal tank and is totally removable as a complete unit, indeed you have to pull it every 7 years to inspect the spar caps for corrosion, there are no access panels in them bar the filler cap and the ony other openings are the vent pipe, Sender unit, fuel supply line and water drain. it forms part of the leading edge……

see

If you would like the complete Piper series manuals on DVD JT442 PM me and I will pop one an old one in the post for you, think the other I gave you was just the Aztec one. if you need the engines too so you can run the Azzy, let me know and will sort that too.

Cessnas such as the 152 have a large wing panel inboard that you remove to reveal a strapped down metal internal tank that can be removed. This is a Cessna removable metal internal tank

JT442

“without external influnces like collision or lightning strikes, the tail assembly is not likely to drop off mid flight”……

I rather thought that there was some suspicion attached to a mid air tail assembly separation on a Dyn Micro Bambi? Not sure that I’ve got the name right.

I don’t want to get the fuel tanks out every week. But, I would like to get them out every three years – or am I being picky?

John Green (This is keeping me away from the rugby)

I give up trying to explain why you don’t need access to some areas. Try this – it seems to be what you’re looking for.

http://beinglatino.files.wordpress.com/2011/01/wonderwomanplane.jpg

Fer cryin’ out loud !

a) I don’t require nor do I solicit support for my opinion – how many times do I have to repeat myself.

b) I do not have a particular problem. If you want to describe my opinion as a ‘problem’ then it is of a non specific nature. It concerns the airframe – any old airframe if it lacks the requisite – as I see it – necessities of access.

Wouldn’t it be much better, cheaper, faster, safer not to remove skins to effect a repair? I accept that in some cases one can’t avoid doing just that, but I guess and it is no more than that, that the majority of repairs can be made using an access hole of adequate dimensions.

I think that you might be mistaken in your view of a/c manufacturers or perhaps any manufacturers. They are:

1. In business primarily for themselves.
2. They are in business to make a profit any which way and how.
3. They will nearly always provide only the bare minimum.
4. If it isn’t specified it won’t be included

That is a bit bleak but I think quite true. They won’t include it in the design if they don’t have to

Well, my Thorpe is 3/4 built and to be fair, does have a huge number of holes… most down to missing skins, BUT I have a large collection of smaller access panels and they are going to fit somewhere… We’ll see. The Thorpe is an odd aeroplane anyway.

As for not being able to reach parts of the rear fuselage – if you can see an issue, then you can effect a repair which may involve replacement of the appropriate skins. There’s not much going on back there, and chances are any defect in the fuselage tubes or bulkhead would require the skins to be removed anyway…. ergo, no panel needed, just periodic inspections every 500 hours (guess!) which require the removal of skin areas (Plus you have those turnbuckle access panels which you can get at least one hand into without issue). You don’t need to access every part of the structure for a pre-flight or 50 hour check. For more in-depth inspections, you may need to remove or replace skin panels, but since its a major inspection there’s no issue. Therein lies the reasons for the varying level of checks and inspections. Without external influence through things like collision or lightning strike (abnormal events), the tailplane is not just going to drop off mid-flight due to an issue which was not identified on your pre-flight or 50 hour inspection. Major issues like that tend to take a long time to develop and they will be identified as a possible hazard during the design stage and factored in to the longer checks as appropriate.

I stand firm with my point ealier about the wing box and tail section – why allow moisture into the structure via a panel when no harm will come of it if it’s built correctly? The manufacturers will know the likely problems with fasteners, materials, structures and fittings in that area and the maintenance schedule should reflect that.

Again, I re-iterate: IF you have found a particular problem with the design, ask the manufacturer about it, oir submit a Mod form. Simple.

I’d be slightly concerned if a main spar inspection required the removal of skins which are connected to the spar, but otherwise you’re looking at investing in a boroscope or fibrescope, a mirror on a stick, and a damn good torch. (or if you’re not an inspector, get them to do it 🙂 )

Finally, leave the lack of access to bag tanks with me for a few minutes and I’m sure I’ll be able to find a couple of examples other than the Jet Provost (just one that I know, and yes, I KNOW its not a comparable airframe…) where the tanks are easilly removable…

Progress 1: (21:37) The Piper range of light aircraft seem to have integral tanks (structural), so you can’t remove the tanks without the wing falling apart unless you trestle and rig the wing. You can see three of the six sides just by looking from the outside, and you can get a mirror into the tank by the filler cap. Any more holes to see the inside, and you’ll struggle to keep fuel in… removal of the tank is possible for detailed inspection / pressure testing, etc, but not pre-flight. The only aircraft I can think of which has panels such as what you want, are the Lancaster and Shackleton where you have 10ft square panels to allow the removal of the rigid tanks. Having removed said tanks, I don’t recommend doing it on a regular basis. (Why would you want to?) There is no facility to look at the top of the tank when it is fitted, and again unless it’s broke, I’m not interested in it.

Progress 2: (21:49) Wing Bladder tanks are actually quite rare these days, especially in home-built aircraft because of the issues regarding their removal. So in the space of 15 minutes, I’ve found a reference to the process of removing one from a Twin Commanche (PA-30). It seems they haven’t got any easier 😉 As per usual, the hole is as small as possible to retain structural integrity whilst allowing access to the tank, IF you have skinny hands and an eyeball on a stalk. Such is life!

4 access panels on the Cessna 182 for access to the bag tanks…

It also appears that you do have support in your quest to a point… alot of engineers are currently complaining about the size of access panels in the integral tanks of Airbus products.

So… now at last I can see what your issue is, BUT I’d still say that maintaining structural integrity is more important than being able to access everywhere.

Mod for a Rans regarding access to the firewall. (non-structural mod) http://www.pipcom.com/~cowcam/rans%20panel%20access.htm

Mentions of a Mod to gain access to Europa aircraft rear fuselages to remedy an issue: http://www.auf.asn.au/airworthiness/AN160807-1.pdf

Here’s a partial quote by a chap named Tom hunter on another forum about modifications to Thorp T18s :
“I am working on a T-18 that has been flying for 34 years and is built according to the plans with regard to no rear access panel. The push pull tube had never been out of the plane and since there is no way to get to that rear bushing in the tube without removing the rudder, the fin and the horizontal stab, it had never seen any service. After 34 years the bushing was frozen in the fitting on the end of the push pull tube. So for those of you who have older Thorps with no access panel on the rear fuselage, you should add one for a couple reasons. One, so you can inspect and service that rear bushing in the push pull tube. Two, so you can inspect the 4130 fittings that your tail wheel mounts to. And three, so you can inspect the jack screw assembly plus lube it. The problems that you will encounter by ignoring the service requirement for the above items are much more real than any imagined loss of skin load carrying capability.

In addition I would urge anyone with an older Thorp to check the rudder for play on the lower hinge. If proper service is ignored for this point, the hole in the lower rudder hinge will become oblong and the bushing will have excessive play. Let this go too long, and you will need to purchase another lower rudder hinge or machine one.

The wing skin templates from John’s shop (years ago) in Burbank did include a 1/8 hole in the top and bottom of the wing directly above the aileron pivot point so in the future if you needed to remove the bolt, you could drill out with a step drill so you could use an extension and socket to remove the pivot bolt to get at the bushing and then install a button cap on the skin when you are finished.”
http://www.thorp18.com/forum/topic.asp?ARCHIVE=true&TOPIC_ID=5794

It seems that the system for detecting issues and then performing modifications does actually work. When you find part of the wing or tail structure developing faults which really requires access to investigate further, highlight a Mod to the inspector, and you shall have access provided that it doesn’t compromise the hull. 😀 I think I’ve vented my spleen enough now, so I shall stop and leave you to your thoughts

JT 442

We operated a Thorp T2-11 for a few years and a fine docile a/c it was apart from a habit of running out of elevator authority in the flare. A touch of power cures that problem. You must be building a different 2-11 to mine. I don’t recall one dozen inspection panels let alone two.

As for the 701, it’s good to see that you’ve done some homework. You’re quite correct about the fuselage access. You can SEE practically everything in both fore and aft directions. But, you CAN’T work on it, because most of it but, not all of it, is out of reach.

The wings and the tail empennage are totally out of bounds. There are no means of access. THAT IS WHAT THIS CONTRIBUTION IS ALL ABOUT. It is not about cutting holes everywhere, it is about delivering a measured response to a real problem. As bawdy as it sounds, I’m not a hole fetishist, I just require to know if there is anything going on that I should know about.

“Pilots NOT prodding around in places that they need to be in is the biggest flight safety issue here”

Chewbydoo.

You’ve got it wrong. The 701 is supplied as a kit without being specified as either microlite or Group A. An electric fuel pump is the difference between microlite and Group A on a Eurostar but not on a 701. The 701 can be certified as either in accordance with its MAUW. At present the 701 divides along the lines of which engine fitted. Group A, Rotax 912, MAUW 499Kg. Microlite, Jabiru 80hp, MAUW 450Kg. Structurally, they are the same – as you correctly write.

Now for something that defies belief. I don’t think that I’ve ever inspected or been able to inspect wing sited fuel tanks. That to me is a serious omission. I’m probably going to be told that there are dozens of a/c with wing inspection panels where it is possible to inspect the fuel tanks on all sides, remove them for perhaps a pressure test, service and clean them and replace. I have never seen this facility on the almost fifty different types of a/c that I’ve flown. I can’t think of anything more critical than not being able – in most cases – to readily gain access to this most vital part of an aeroplanes anatomy. It really is too important to be left to chance and hope.
If nothing else, this is a facility that should be available on all GA aircraft

It is not JUST a question of inspection. Any aperture should be of a size that permits the use of tools to enable a repair to be effected. Anything less is a waste of time.

John Green

Either way, I’d follow the pre-flight inspection word for word, plus anything extra which you are aware of and is accessible. Chopping holes in an aeroplane is generally a bad idea, as id deviating from the routines specified in the relevant maintenance / inspection manual.

Pilots prodding around in places they don’t need to be is the biggest flight safety issue here. (Unless you believe there is cause for genuine access, in which case submit a modification request and grab your drill…..)