Least resource intensive/easy to maintain aircraft of WW2?

FLYBOYJ said:

Absolutely not!

Although a simple aircraft, pulleys, cables and bellcranks need to be lubricated, the airframe itself needs to be periodically inspected, especially if one is performing aerobatics. Read about the maintenance of fabric aircraft and what goes into them, lastly we have some wood in the structure, very labor intensive depending on the environment where the aircraft is being operated. Are you getting the picture? I haven't even gotten into the engine! Engine oil - 25 to 50 hour changes. Inspections - 50 to 100 hour. I believe a few of our members have actually turned wrenches on the Moth so I know they'll chime in.

No - even the simplest of aircraft cannot go for "hundreds of hours" without some kind of maintenance!

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A Tiger Moth is very old tech. A gifted and diligent amateur can keep one flying, there are estimated to be around 250 still flying. Compare to something like a Boeing 777. The major service intervals on a 777 are months apart, even a walk around inspection looking for obvious faults, damage leaks etc done after every landing can represent hours and thousands of miles. The 777 will easily do in a couple of days the hours and miles that some Moths do in a year, but that doesnt mean anything is easy or cheap.

I remember reading in Michael Korda's With Wings like Eagles, the Hurricane with its large areas of canvas, was an easier transition for ground crew familiar with working on Canvas biplanes.

Fair points, and I exaggerate on the hours. My thinking was an in-line, poppet valve, air cooled four that's been produced for years and in common civilian use would not have the cooling system, sleeve valves, radial cylinder oil flood, and a dozen or more pots and their dozens of grease points, and other maintenance issues associated with larger, more complicated engines. But I don't mean to suggest the Moth's engine can be neglected, and make no assumptions of its airframe and controls.

Compared to other single engined RAF aircraft of its era, say Typhoon or Spitfire, I have to think the Tiger Moth would be easier and less time consuming for our mechanic to complete maintenance on engine and cooling systems. As for a total engine rebuild, a DH Gipsy Major must be a dream compared stripping down and rebuilding a 24 cylinder, sleeve valve Napier Sabre. That's where I was going.

pbehn said:

A Tiger Moth is very old tech. A gifted and diligent amateur can keep one flying, there are estimated to be around 250 still flying. Compare to something like a Boeing 777. The major service intervals on a 777 are months apart, even a walk around inspection looking for obvious faults, damage leaks etc done after every landing can represent hours and thousands of miles. The 777 will easily do in a couple of days the hours and miles that some Moths do in a year, but that doesnt mean anything is easy or cheap.

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There's no comparison as both aircraft are at the far end of their maintenance categories and if a 777 is in service maintenance is determined mainly by flight hours although there are calendar maintenance requirements as well. (I never got to work on 777s but I have worked on DC-10s, MD-11s and 757s to name a few). If you know what you're doing you don't have to be "gifted" to maintain a Tiger Moth, just diligent and dedicated. This goes for any classic aircraft or warbird.

Bottom line, one needs to look at the maintenance programs for the specific aircraft, even a "simple" aircraft like a Tiger Moth requires periodic maintenance and many times you'll looking at hourly intervals that can be as little as 25 hours. In the US, at a bare minimum, items listed in FAR 43 appendix D is a guideline for 100 and annual inspections.

Admiral Beez said:

Fair points, and I exaggerate on the hours. My thinking was an in-line, poppet valve, air cooled four that's been produced for years and in common civilian use would not have the cooling system, sleeve valves, radial cylinder oil flood, and a dozen or more pots and their dozens of grease points, and other maintenance issues associated with larger, more complicated engines. But I don't mean to suggest the Moth's engine can be neglected, and make no assumptions of its airframe and controls.

Compared to other single engined RAF aircraft of its era, say Typhoon or Spitfire, I have to think the Tiger Moth would be easier and less time consuming for our mechanic to complete maintenance on engine and cooling systems. As for a total engine rebuild, a DH Gipsy Major must be a dream compared stripping down and rebuilding a 24 cylinder, sleeve valve Napier Sabre. That's where I was going.

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Exactly

FLYBOYJ said:

There's no comparison as both aircraft are at the far end of their maintenance categories and if a 777 is in service maintenance is determined mainly by flight hours although there are calendar maintenance requirements as well. (I never got to work on 777s but I have worked on DC-10s, MD-11s and 757s to name a few). If you know what you're doing you don't have to be "gifted" to maintain a Tiger Moth, just diligent and dedicated. This goes for any classic aircraft or warbird.

Bottom line, one needs to look at the maintenance programs for the specific aircraft, even a "simple" aircraft like a Tiger Moth requires periodic maintenance and many times you'll looking at hourly intervals that can be as little as 25 hours. In the US, at a bare minimum, items listed in FAR 43 appendix D is a guideline for 100 and annual inspections.

14 CFR Appendix D to Part 43 - Appendix D to Part 43—Scope and Detail of Items (as Applicable to the Particular Aircraft) To Be Included in Annual and 100-Hour Inspections

www.law.cornell.edu

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Agreed, thats actually what I was trying to point out. In flight a 777 may have only two moving parts to keep it going, that doesnt mean its jet engines arent complex. When the Moth first flew, people used to write into newspapers if their car did 100,000 miles, now we expect a car to do that with no major issues.

pbehn said:

Agreed, thats actually what I was trying to point out. In flight a 777 may have only two moving parts to keep it going, that doesnt mean its jet engines arent complex. When the Moth first flew, people used to write into newspapers if their car did 100,000 miles, now we expect a car to do that with no major issues.

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I think car reliability plateaued in the 1990s. In the 1970s driving a car from NYC to SF was a little risky. By the 1990s, with fuel injection, electronic ignition, oil tight valve guides, rings and engine seals, hydraulic tappets, steel belted tubeless tires, air conditioning and reliable cooling, you'd drive your Toyota Camry from NYC to SF and back a dozen times without a thought. Nowadays, if my 2022 VW doesn't give me a damn error code before I left the state or province I'm grateful.

Well, it is not Toyota's fault you bought a VW . . .

Around 1930 DH was running full page advertisements to announce that one of their engines had made 500 hours with all the valves and valve springs working. A lot of the American small 5 cylinder radials were only good for a few hundred hours before overhaul. The engine companies would sometimes sell the overhaul kits to the owner (An A&P mechanic, what's that?) A 1918 Curtiss Jenny might need the heads pulled every 20 hours or so to scrape the carbon off them( although might be the quality of the fuel. Many of the Pre WW II engines and many of the WW training engines used a host of grease fittings on the engines. No check the oil and add few quarts after a long flight. More like pull the cowl and go over a number of things between flights.
I had a 1970 Ducati 350 Desmo aside from things like tightening the chain the suggested maintenance schedule was 1000 Km for many things and even the valves were supposed to adjust every 2000 Km if I remember right ( could very well be wrong, but I put about 10,000 KM on it in about 6 months so there was a LOT of bolt tightening.

The work on an old airplane may not be difficult for each task, you just have to perform each task 3-4 times as often as on a 1980s light plane.

Shortround6 said:

The engine companies would sometimes sell the overhaul kits to the owner (An A&P mechanic, what's that?)

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Actually A&P licenses (back then I believe they were called "A&E licenses") were first issued in 1927

One of the 5 cylinder engines showed up in 1926 and it was copied (to try to fix reliability problems) in 1928.

It was used in some other planes but the 2nd engine was used in the Monocoupes.

There were a few other 5 cylinder radials that might have more or less kinship to the original.

The rocker arms on close up pictures show a grease fitting on each rocker arm.

Now think about Lindbergh flying 33 hours over open ocean in 1927.

Just a wee bit on what was the least maintenance intensive aircraft, I dunno the answer to that, but I know that the German fighters, the Bf 109 and Fw 190 were particularly easy to maintain because of access to their engines and vital systems. The Bf 109's engine cowls, for example are much easier to open and provide really good access compared to the Spitfire and Hurricane. Regarding engines, the Napier Sabre :eyeroll: was a particularly maintenance intensive engine, with twice the number of plugs as most other aircraft, plus its chronic unreliability, even when they did fix the sleeve issues. In a modern setting, from what I've learned the Daimler Benz engines are dogs to maintain and are also less reliable than Merlins in the Bf 109 airframe. The Buchon makes maintenance easier, that's for sure. Mind you, there is a whole industry supporting Merlins today.

Those Haynes Manuals on aircraft types are really informative and provide detailed information about each aircraft type. Well worth digging out if you wanna find out about your favourite WW2 aircraft and you don't have one in your backyard...

On the subject of maintaining aircraft, yes, a Tiger is much easier to maintain than even a WW2 fighter because it is simple. There's no hydraulics, air con systems, it has simple electrics and fixed taildragger undercarriage, so no complicated nosewheel steering mechanisms, for starters.

Aircraft maintenance has changed a shed-ton, not just because of advances in technology. Every aircraft needs maintenance, but the thing is how often, which is nominally decided by how many cycles (take-offs and landings) or the passing of time. In the airline world of highly regulated maintenance schedules, everything has been pre-decided and the maintenance bodies work to what the manufacturers stipulate. Airlines employ alphabet check system, which are dependent on time between inspections. A-chks are every 500 flight hours and so forth. Most regional and medium sized jets have A and C-chks, which occur every 18 months to two years, whereas your big jets have B and D-chks, which take place every four years or so. There are smaller inspections, Line Chks (every week to two weeks) and overnight inspections, which are nominally decided on by the operators.

One thing that used to be a thing in the immediate post war period was that airlines used to bring their aircraft in for maintenance on tight schedules, but some operators did everything on every inspection, which is simply unnecessary. At one time (I'm a bit vague on the details now) a group of airlines and aircraft manufacturers got together to revise maintenance standards across the industry, calling themselves the Maintenance Steering Group. MSG still operates to this day and aids in refining maintenance. For example, there's no need to rip the entire aircraft apart and remove everything with every maintenance check if not all components are worn or damaged. For a cost-conscious industry such as the airlines, it's just a waste of money and doesn't guarantee any greater degree of safety or reliability. The concept of time-expired parts came about from all this, too, which makes maintenance easier and spreads cost across TBOs, which saves money in the long run.

In WW2 obviously things were different and less defined, but there was a war on, so normal procedures went out the window in terms of manpower, working hours, supply of parts etc.

The Russians emphasized maintenance in their design bureaus, and while not consistent, they frequently succeeded. Note the lower degrees of technology familiarity of the population, vs US, Brits, Germans, Japanese. Add to that the terrible weather and primitive airfields on Eastern Front. Note that many post war Asian and African countries used An-2s for logistics versus DC-3s or Ansons, also available affordably. I had an opportunity to fly in them around small Eastern European places in the '80s, and someone said that 'you could maintain it with a hammer!' Close to being true.
There are several analyses of Me109 vs FW190 operations. Willy designed things like thoroughbred sprint race cars, while Kurt seemed to look at endurance races. Bits in the Me were squeezed into watchmaker sized slots while the Fw engine peeled away with four bolts, with easy access to all accessories. Also note how easily the Fw190 could take on and off modules, and adapt to a WIDE variety of roles.
Also consider the standout light bombers of WWII ... the B-25, B-26 and A-26. They had different specs initially, but all wound up performing many similar roles. The Martin was complex, and had a seven man crew, with features like a heavy bomber. The Douglas was a race horse, with a three man crew, relying on speed over guns with the same engines. The North American was a mix and the earliest, with 5 crew and less powerful engines, but few hydraulics or fussy systems. Well into the '60s, the Air Force kept them in service for their ease of maintenance, using them in utility and flight proficiency roles. Sadly, that simplicity also made them attractive to Caribbean drug runners, with many of the survivors scattered over small fields in the South, or at the bottom of the Gulf of Mexico.

Just a collection of circumstances for your consideration.

Cheers, Bob

Admiral Beez said:

Compared to other single engined RAF aircraft of its era, say Typhoon or Spitfire, I have to think the Tiger Moth would be easier and less time consuming for our mechanic to complete maintenance on engine and cooling systems.

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A bit of a silly argument, the Tiger Moth wasn't a WW2 combat aircraft not was it ever a combat aircraft, it doesn't matter that it was easier to service and maintain than a Spitfire or Typhoon because it couldn't fulfill any combat roll that any combat aircraft in WW2 did, you want performence you pay for it.

nuuumannn said:

On the subject of maintaining aircraft, yes, a Tiger is much easier to maintain than even a WW2 fighter because it is simple. There's no hydraulics, air con systems, it has simple electrics and fixed taildragger undercarriage, so no complicated nosewheel steering mechanisms, for starters.

Aircraft maintenance has changed a shed-ton, not just because of advances in technology. Every aircraft needs maintenance, but the thing is how often, which is nominally decided by how many cycles (take-offs and landings) or the passing of time. In the airline world of highly regulated maintenance schedules, everything has been pre-decided and the maintenance bodies work to what the manufacturers stipulate. Airlines employ alphabet check system, which are dependent on time between inspections. A-chks are every 500 flight hours and so forth. Most regional and medium sized jets have A and C-chks, which occur every 18 months to two years, whereas your big jets have B and D-chks, which take place every four years or so. There are smaller inspections, Line Chks (every week to two weeks) and overnight inspections, which are nominally decided on by the operators.

One thing that used to be a thing in the immediate post war period was that airlines used to bring their aircraft in for maintenance on tight schedules, but some operators did everything on every inspection, which is simply unnecessary. At one time (I'm a bit vague on the details now) a group of airlines and aircraft manufacturers got together to revise maintenance standards across the industry, calling themselves the Maintenance Steering Group. MSG still operates to this day and aids in refining maintenance. For example, there's no need to rip the entire aircraft apart and remove everything with every maintenance check if not all components are worn or damaged. For a cost-conscious industry such as the airlines, it's just a waste of money and doesn't guarantee any greater degree of safety or reliability. The concept of time-expired parts came about from all this, too, which makes maintenance easier and spreads cost across TBOs, which saves money in the long run.

In WW2 obviously things were different and less defined, but there was a war on, so normal procedures went out the window in terms of manpower, working hours, supply of parts etc.

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Hi
The way maintenance was done changed during WW2, the Air Ministry's book 'Operational Research in the RAF' has some info on this reference Coastal and Transport Commands:



Mike

Several comments: We seem to have wandered far afield. To compare maintainability, you have to compare like to like ... aircraft that perform the same role. (not roll, btw) Comparing a Cub to a Concorde is ridiculous.

Second, we must consider the whole maintenance picture from parts supply chain to aircraft ready to go on the flight line. A single source manufacturer unable to keep up demand for unique and critical winglenuts will keep a whole wing of strategic bombers grounded in North Dakota. Also, do they need special tools or skills. The '60s A-5 Vigilante designers considered the complexity of their supersonic nuclear bomber, and designed a companion trouble shooting cart that could plug in and diagnose tricky systems ... much like the computerized auto diagnostic bench machines of the '80s, now reduced to hand helds. The only problem is the North American testing unit, the size of a tiny car, was susceptible to salt air, and crews spent more time trouble shooting the test unit than the airplane.
McDonnell designed the F-4 Phantom to be maintained aboard Navy ships with limited access to parts warehouses, so used the same fuel transfer pump in multiple locations ... needed to move JP between the many internal tanks and up to three external droppable tanks. The problem arose when the Air Force found their dozens of fighter bomber designs developed in the '50s unsuitable for wars like Viet Nam, and also ordered the Navy Phantom. Their supply philosophy had the AF order several years of pumps in advance of the need, and suddenly there were none available for the Navy as the AF had the plants locked up with production contracts. We found Navy and Marine aircraft unable to carry more than one external tank, and sometimes none ... just because they didn't have enough transfer pumps on hand.
Touching on the Spitfire vs. Hurricane issue, despite using the same Merlin, Mitchell based his machine on elegance and lightness, using stressed skin, aluminum monocoque construction, much of it with compound curves requiring special tools and skills to form ... like a thoroughbred race car. By contrast, the Hurricane used welded steel tube structure, and skins were not structural ... just tacked on with screws or Dzus fasteners, or even fabric over wood stringers. It should be obvious which would absorb more punishment, and be easier to repair ... also requiring less skills or tools.
Finally, Jeffery Quill's "Sigh for a Merlin" describes the difference between the Rolls Royce built Merlins, and those licensed to Packard and US manufacturers. The British tooling and techniques had sloppiness and variations in them, and those assembling engines were diligent craftsmen, measuring and matching things like pistons to fit bores and with equal weights. Beautiful work, but time and skill intensive. American machine tools were much more precise, and this hand fitting and matching was dispensed with.
Cheers, Bob

fannum said:

Finally, Jeffery Quill's "Sigh for a Merlin" describes the difference between the Rolls Royce built Merlins, and those licensed to Packard and US manufacturers. The British tooling and techniques had sloppiness and variations in them, and those assembling engines were diligent craftsmen, measuring and matching things like pistons to fit bores and with equal weights. Beautiful work, but time and skill intensive. American machine tools were much more precise, and this hand fitting and matching was dispensed with.
Cheers, Bob

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Oh no, not this again?

fannum said:

Several comments: We seem to have wandered far afield. To compare maintainability, you have to compare like to like ... aircraft that perform the same role. (not roll, btw) Comparing a Cub to a Concorde is ridiculous.

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Agree

fannum said:

Second, we must consider the whole maintenance picture from parts supply chain to aircraft ready to go on the flight line. A single source manufacturer unable to keep up demand for unique and critical winglenuts will keep a whole wing of strategic bombers grounded in North Dakota. Also, do they need special tools or skills. The '60s A-5 Vigilante designers considered the complexity of their supersonic nuclear bomber, and designed a companion trouble shooting cart that could plug in and diagnose tricky systems ... much like the computerized auto diagnostic bench machines of the '80s, now reduced to hand helds. The only problem is the North American testing unit, the size of a tiny car, was susceptible to salt air, and crews spent more time trouble shooting the test unit than the airplane.
McDonnell designed the F-4 Phantom to be maintained aboard Navy ships with limited access to parts warehouses, so used the same fuel transfer pump in multiple locations ... needed to move JP between the many internal tanks and up to three external droppable tanks. The problem arose when the Air Force found their dozens of fighter bomber designs developed in the '50s unsuitable for wars like Viet Nam, and also ordered the Navy Phantom. Their supply philosophy had the AF order several years of pumps in advance of the need, and suddenly there were none available for the Navy as the AF had the plants locked up with production contracts. We found Navy and Marine aircraft unable to carry more than one external tank, and sometimes none ... just because they didn't have enough transfer pumps on hand.

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You bring up good points and I know, with your time as a military aviator probably experienced this many times. I think what we have is many combat aircraft designed during the 1950s were not "maintenance friendly" and were probably looked upon as expendable as the nuclear option was always looked at "choice A" for the next major shooting war by those with stars on their shoulders. As far as "The problem arose when the Air Force found their dozens of fighter bomber designs developed in the '50s unsuitable for wars like Viet Nam, and also ordered the Navy Phantom" well that's just not the case. The USAF was interested in the "McDonnell F-110" (F-4C) as early as 1962, the first Air Force Phantom flew on 27 May 1963, the first USAF F-4 unit reached Vietnam sometime in 1964 IIRC. The major airframe manufacturers of the day (Lockheed, "MacDac" Northrop and Grumman) for one reason or another did not have the foresight (and no fault to them) to adjust their logistic systems to sustain advanced combat aircraft in a prolonged conventional conflict. In lessons learned after Vietnam, logistic support and life cycle sustainment was built into many future contracts, I believe the F-14 was the first aircraft built under this new mindset.

fannum said:

Touching on the Spitfire vs. Hurricane issue, despite using the same Merlin, Mitchell based his machine on elegance and lightness, using stressed skin, aluminum monocoque construction, much of it with compound curves requiring special tools and skills to form ... like a thoroughbred race car. By contrast, the Hurricane used welded steel tube structure, and skins were not structural ... just tacked on with screws or Dzus fasteners, or even fabric over wood stringers. It should be obvious which would absorb more punishment, and be easier to repair ... also requiring less skills or tools

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For the most part agree. If large portions of fabric had to be replaced, there is a process that required an environmentally controlled facility (depending on ambient weather conditions). This could have be problematic in the field.

fannum said:

Finally, Jeffery Quill's "Sigh for a Merlin" describes the difference between the Rolls Royce built Merlins, and those licensed to Packard and US manufacturers. The British tooling and techniques had sloppiness and variations in them, and those assembling engines were diligent craftsmen, measuring and matching things like pistons to fit bores and with equal weights. Beautiful work, but time and skill intensive. American machine tools were much more precise, and this hand fitting and matching was dispensed with.
Cheers, Bob

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This is hogwash - there been much discussion about this on this site with many folks providing documented evidence to say otherwise. We also have members who have turned wrenches on Merlins who can chime in.