What factors make some airplane easier to build than others?

[Nodeo-Franvier]

I have often read that fighter like Bf-109,He-100,Dewoitine d.520 etc. Incorporate new technology/features that make them faster/easier to build than something like Macchi c.200,MS406,A6M,Spitfire etc.
What does these difference come down to?

 

[GregP]

As a WWII aircraft restorer, I can say it comes down to design for manufactuability.

If you design something that has easy-to-access riveting, you can build it a LOT faster than something that reguires special tooling and 4 fot 11 inch female to reach the rivets.

By way of example, a Van's RV-4 wing is simple to build, requiring no special access or tools, The end aircraft is fast and aerobatic.

It also has simple structures that make it a fast build. All the ribs are the same size and all are riveted similarly. The fuselage has relatively easy curves and access for construction. Basically, a rectangular or double-taper wing is a LOT easier to build than an elliptical wing.

A Silence Twister is made from composite, making it similarly easy to build, albeit different techniques. See below.

But if it were made of aluminum, there would be a lot of different parts that require difficult access and special tools. Shaping the fuselage would also not be simple.

So, it boils down to whether or not the designer took assembly into account when designing the aircraft.

 

[pbehn]

Three things I can think of before anything specific is mentioned.
1, How many do you expect to make.
2 How much experience do you have
3 How many compromises to performance can you get away with for ease of production.

 

[PFVA63]

Hi,
In addition to what others have already posted I belive there are a number of issues that can also play a part, including (potentially) some of the following;

• Limiting compound curvatures
• Elimination, or simplification of wing fillets
• Reduction in number of parts
• Easy access to internal areas

With regards to the first bullet, somewhere I once read that the Hawker Hurrican was easir to build and easier to repair in some cases than the Supermarine Spitfire because its wings were simpler in form than those on the Spitfire, where individual panels could potentially have curvature in two directions, making it more time consuming to both manufacture and replace in the event of damage.

With respect to the second bullet, many low wing aircraft (especially single engine ones) often had fillets with compound curvature in way of where the wing root meets the fuselage (see for example the P-40, Spitfire, SBD, TBD, Hurricane, etc). Other planes, however, including many mid wing planes instead had there wing roots intersect the fuselage at a sharp 90 degree (or near 90 degree) angle, such as the Corsair, Wildcat, Hellcat, Buffalo, TBF and the like). The elimination of needing to fit the fillets (which the complex, compound curvature shapes) would theorectically reduce the time required for both building and potentially repair as well.

With respect to the third bullet, although not airplane related, I once bought a car which was in its last model year of production, and in looking through it you could see several areas where the company that built it worked to simplify the design to cut down on the number of individual steps required to assemble it. The main one that stuck out to me being that instead of having a 60/40 split fold-down rear seat, the rear seat back was one single piece that could be folded down. While it might not seem like replacing the two smaller sections of seat back with one larger one would make a whole lot of difference, in reality it meant that on the production line, you only had to install (and align) two hinges instead four, which cuts out several steps in the process.

For an airplane, a similar situation could be something as simple as leaving a tail wheel non-retractable, instead of having to fit the mechanism, controls, and potentially hinged doors, that a retractable wheel would/could require.

And finally, with respect to the last bullet, issues such as the thickness of a wing may potentially make it easier/or harder to fit (and repair) items internal to the wing such as guns, control cables, fuel tanks (and protective coverings), etc

Regards

Pat

PS. Also with respect to the A6M I believe that I read somewhere that to help lighten the plane as much as possible many of the larger structural members had "lightening hole" cut outs in them, which takes time to cut or form than webframes without lightening holes.

 

[Glider]

It is a good question. The 109 and the Spitfire were very close in performance. Yet the 109 was designed to be easily built but this was a secondary concern for the Spitfire. When the British had the opportunity to closely examine the 109 they were very complimentary about the various features built into the design of the 109 that made it easier to build and maintain.

The following may be of interest

 

[GregP]

Hi,
In addition to what others have already posted I belive there are a number of issues that can also play a part, including (potentially) some of the following;

• Limiting compound curvatures
• Elimination, or simplification of wing fillets
• Reduction in number of parts
• Easy access to internal areas

With regards to the first bullet, somewhere I once read that the Hawker Hurrican was easir to build and easier to repair in some cases than the Supermarine Spitfire because its wings were simpler in form than those on the Spitfire, where individual panels could potentially have curvature in two directions, making it more time consuming to both manufacture and replace in the event of damage.

With respect to the second bullet, many low wing aircraft (especially single engine ones) often had fillets with compound curvature in way of where the wing root meets the fuselage (see for example the P-40, Spitfire, SBD, TBD, Hurricane, etc). Other planes, however, including many mid wing planes instead had there wing roots intersect the fuselage at a sharp 90 degree (or near 90 degree) angle, such as the Corsair, Wildcat, Hellcat, Buffalo, TBF and the like). The elimination of needing to fit the fillets (which the complex, compound curvature shapes) would theorectically reduce the time required for both building and potentially repair as well.

With respect to the third bullet, although not airplane related, I once bought a car which was in its last model year of production, and in looking through it you could see several areas where the company that built it worked to simplify the design to cut down on the number of individual steps required to assemble it. The main one that stuck out to me being that instead of having a 60/40 split fold-down rear seat, the rear seat back was one single piece that could be folded down. While it might not seem like replacing the two smaller sections of seat back with one larger one would make a whole lot of difference, in reality it meant that on the production line, you only had to install (and align) two hinges instead four, which cuts out several steps in the process.

For an airplane, a similar situation could be something as simple as leaving a tail wheel non-retractable, instead of having to fit the mechanism, controls, and potentially hinged doors, that a retractable wheel would/could require.

And finally, with respect to the last bullet, issues such as the thickness of a wing may potentially make it easier/or harder to fit (and repair) items internal to the wing such as guns, control cables, fuel tanks (and protective coverings), etc

Regards

Pat

PS. Also with respect to the A6M I believe that I read somewhere that to help lighten the plane as much as possible many of the larger structural members had "lightening hole" cut outs in them, which takes time to cut or form than webframes without lightening holes.

Just to sort of address fillets specifically, they are relatively easy to make for production since you have molds and stamp them out. Yes, people have to attach the 1/4-turn Dzus fastener hardware, but that's easy compared with making identical compound curves by hand.

I have taken off and installed many fillets on warbirds and they are decently easy to deal with. Even replacing Dzus hardware isn't all that bad compared with hand-forming a good fillet. I can make any sort of curve you want, but making two identical mirror images is another story (I can get close, but that isn't production standard)... better make molds and stamp them!

Cheers!

 

[Shortround6]

A lot of it relates to what Greg is saying.
Yes the 109 was designed to be easy to make. However in the early years they were making it not by the hundreds in one big factory but by the scores in a 1/2 dozen little ones.
I wonder what the cost of tooling up 6 different production lines was?

Bf 109B production
BFW (Augsburg)....76
Erla.............................175
Fieseler.....................90

Bf 109C/D production
BFW (Augsburg)........62
Focke-Wulf................123
Erla................................168 (RM 85,000)
Fieseler..........................80
AGO..............................128
Arado/W.....................144

Granted in may have helped set up the factories and work force to make other things.
There can be a lot of stuff 'hidden' in official prices.

Or look at the US.
P&W built/operated 4 satellite factories in Connecticut during WW II (and for many years afterwards) I worked in one for 4 years in the 70s. over 90 % pf the machinery had brass tags saying "property of the USN". P&W bought the machines surplus after WW II in the post war cutbacks but during the war P & W was making thousands of engines on machinery that P & W didn't pay for. How do you figure out what the cost of a P & W engine was?
In their defense P & W "licensed" the R-1830 to Buick and Chevrolet for $1.00 an engine stopped collecting even that part way through the war. Same for the R-2800s made by Ford and others.
Trying to untangle the accounting 80years later would be quite an undertaking.

 

[FLYBOYJ]

I wonder what the cost of tooling up 6 different production lines was?

Something I was about to bring up but you beat me to it.

A lot of good information here and we can talk about manufacturing smaller detailed parts but aircraft are not hand built. They are built on assembly jigs.

This tooling is the heart and soul of the production line. You can "hand build" aircraft but you're never going to produce them in mass quantities with out assembly jigs which can be very expensive to build and maintain.

Photos credit the internet

 

[PAT303]

It also depends on where they are getting made. The Americans made enormous buildings with planes coming off the line hourly because they were not under constant bombing, the Germans and British had much smaller buildings with scattered satellite factories feeding them, I wonder how many man hours there was transporting parts between them, likewise lost due to bombing?, was that time added to the production hours?.

 

[pbehn]

It is a good question. The 109 and the Spitfire were very close in performance. Yet the 109 was designed to be easily built but this was a secondary concern for the Spitfire. When the British had the opportunity to closely examine the 109 they were very complimentary about the various features built into the design of the 109 that made it easier to build and maintain.

The following may be of interest

View attachment 698576View attachment 698577View attachment 698578View attachment 698579View attachment 698580View attachment 698581

The goings on of the Air Ministry and the RAF are amusing at times. Did they do such an investigation into such things before they issued the first order for 300 Spitfires? Did anyone consider that if war did come they would need thousands per year not hundreds? Part of the design problem Mitchell had was fitting 8 Mgs into the design, the Bf 109 didnt have this issue. In choosing the design Mitchell did, the Spitfire could eventually fit canon in the wings with blisters, And then there is the thorny issue of gun heating, requested after the contract was placed. Oh and can we have a long range PR version please? Almost the moment war was declared they all sides realised they were blacked out from news about the opposition, especially their fleets, nothing could be more obvious or logical as a consequence of declaring war, yet no one did anything about it until it happened.

 

[tomo pauk]

And then there is the thorny issue of gun heating, requested after the contract was placed.

Whose job was to make sure that guns function between SL and service ceiling - costumer's or manufaturer's?

 

[pbehn]

Whose job was to make sure that guns function between SL and service ceiling - costumer's or manufaturer's?

In my opinion the customer, the plane maker neither makes guns nor specifies which guns are needed.

 

[tomo pauk]

In my opinion the customer, the plane maker neither makes guns nor specifies which guns are needed.

Spin it anyway you want, and have a good life.

 

[pbehn]

Spin it anyway you want, and have a good life.

Well some guns didnt work anyway regardless of how well they were heated, sometimes the fault of the gun, sometimes the fault of lubricants used or poor maintainance, When guns didnt fire under high G loading the solution was with the gun orientation and feeding, a plane manufacturer can be involved in the discussion but it cant start re designing the guns or the feed, if they do the gun manufacturer isnt responsible for what happens next.

 

[FLYBOYJ]

Whose job was to make sure that guns function between SL and service ceiling - costumer's or manufaturer's?

It depended on the contract. In the US sometimes the government dictated certain equipment to be installed on the aircraft (like guns)

 

[tomo pauk]

It depended on the contract. In the US sometimes the government dictated certain equipment to be installed on the aircraft (like guns)

Fighter aircraft, like Spitfire, tended to have guns installed.
If these don't work at 25000 ft on one aircraft, while work on another aircraft, who botched the job: costumer, or manufacturer of a said fighter?

 

[FLYBOYJ]

Fighter aircraft, like Spitfire, tended to have guns installed.
If these don't work at 25000 ft on one aircraft, while work on another aircraft, who botched the job: costumer, or manufacturer of a said fighter?

Yes, but who directed the installation? .303s or 20mm or whatever the manufacturer feels like?

Usually it goes back to the gun manufacturer especially if the installation met engineering requirements, which means the guns were installed properly.

 

[Shortround6]

In the mid 30s next to nobody was specifying gun heaters.
1, Nobody was flying much higher than they did in WW I and if they did they fly for long at that altitude.

for the British

Went into first squadron service in Feb 1937.

Note that fuselage mounted guns already had heaters.
Also not that the British, in the 1930s, often only carried out gunnery practice once or twice a year and usually in good weather (summer or at least not winter) and the target towing planes were not flying at high altitude. They simply didn't have the experience to tell them they needed heat for the guns.
The Americans were no better. The .50 cal guns didn't work in the early P-40s for several reasons despite a single .50 being mounted, supposedly as "standard" since about 1930 in most US fighters, both army and navy. 10 years and the British were the ones that discover it didn't work as a cowl gun? (won't get into the wing guns)

 

[pbehn]

In the mid 30s next to nobody was specifying gun heaters.
1, Nobody was flying much higher than they did in WW I and if they did they fly for long at that altitude.
View attachment 698708
for the British
View attachment 698709
Went into first squadron service in Feb 1937.

Note that fuselage mounted guns already had heaters.
Also not that the British, in the 1930s, often only carried out gunnery practice once or twice a year and usually in good weather (summer or at least not winter) and the target towing planes were not flying at high altitude. They simply didn't have the experience to tell them they needed heat for the guns.
The Americans were no better. The .50 cal guns didn't work in the early P-40s for several reasons despite a single .50 being mounted, supposedly as "standard" since about 1930 in most US fighters, both army and navy. 10 years and the British were the ones that discover it didn't work as a cowl gun? (won't get into the wing guns)

S/R did guns become more sensitive? Maybe changes to get a better rate of fire? In WW1 guns were outside the cowl or even on the upper wing?

 

[Shortround6]

A lot of the guns "froze" which is actually the oil/lubricants getting too cold rather than actual water problem.
Depending on the oil/lubricants which were much thinner than engine oil, the guns should have worked at sub-zero temperatures. How much sub-zero was the question. 5 degrees or 30 degrees below? The later was a real problem.
Army Machine guns had certainly worked during winter weather during WW I.
Once you get the gun to fire a few times it will warmup pretty quickly.

Finns and Russians figured things out before the war. They removed all traces of lubricant and accepted the increase wear.