# Why is there typically a large gap between the first flight and mass production of aircraft?

Here are some examples I've found on Wikipedia:

Me-262: first flight 1942 July, introduced 1944 April.

MiG-19: first flight 1953 Sep, introduced 1955 March.

Dassault Mirage III: first flight 1956 November, introduced 1961.

F-4 Phantom: first flight 1958 May, introduced 1960 December.

This shows a two or three or even five year gap between the first flight and the entering into mass production.

Why such a long gap? What goes on during those years? To me it seems like once the first flight is done, it "works" and the only thing left is some finishing touches. Is it possibly more a matter of setting up a factory?

• Cars are very simple in comparison to aircraft, yet there can often be 18-24 months of testing between the first roll-out of a pre-production car and the first production model rolling off the line. There is an incredible amount of testing necessary to ensure that all the theoretical guesses that went into the design actually work in practice. – FreeMan Jun 3 '16 at 12:34
• Also, 21 months to get the first jet engined aircraft ever flown from first flight to production, during a war, doesn't seem like very long at all! – FreeMan Jun 3 '16 at 12:40
• @FreeMan Depends on how you look at it. I'm sure many in the Luftwaffe felt like it was an eternity, precisely because it was during a war (when they needed everything yesterday). I chose the Me-262 because, despite being an early combat jet, it seems to fit the pattern. – DrZ214 Jun 5 '16 at 5:43

You don't want an aircraft that just 'works'- rather, you want an aircraft that satisfies your needs. The first flight is usually made by a prototype and does just that- it flies and pretty much nothing else.

Only once you start the flight tests do you understand the airframe limitations and whether the aircraft meets the requirements; usually, a number of modifications are needed. Also, the first flights are rarely, if ever in production configuration. In most of the cases, the required systems are fitted later. In general, most of the combat aircraft bring about substantial improvement over its predecessors- in fact it is a requirement, as the old ones can be used with small improvements at a much lesser cost.

Me 262 was really a revolutionary product and the use of jet engines caused a number of delays; in fact the prototypes were flight tested with piston engines in 1941. The first test flight happened with piston engine- just as well because both the jets flamed out soon after takeoff. By the time the second and third prototypes, the engines had been changed. However, these engines (Jumo 004) were larger, requiring larger nacelles, which in turn required a bigger vertical stabilizer (the landing gear was changed later). Pre-production of Me 262 had started in 1943 (and went nowhere due to engine troubles) when it was decided to change it into a bomber, further increasing the development period. By the time it took the field, it was in too few numbers to do anything.

Another example is the Mirage III. There were significant differences between the aircraft in first flight and the production one. The prototype never reached the required Mach 2 in level flight.The first one to do was the pre-produciotn Mirage IIIA with an engine with more than 30% extra thrust, lengthened fuselage for radar etc. Even this version was not combat capable- that was the Mirage IIIC.

The design is not frozen till the flight testing is over and the production plans can only be finalized after that- you never know what'll change (for example the hugely successful Su-27 underwent a change in wing design midway through testing). The delays due to setting up of production comes later and is normally quite less for countries/companies having experience. It is the design freeze that takes up more time during test flights.

• Only once you start the flight tests do you understand the airframe limitations and whether the aircraft meets the requirements; usually, a number of modifications are needed. Can you elaborate on this more? My understanding is that wind tunnels can be run at any speed with the model at any angle of attack, so what airframe limitations are only discoverable in actual flight? – DrZ214 Jun 3 '16 at 7:44
• @DrZ214 I'm talking about the aircraft performance (speed, response etc.) in total. Though the wind tunnels and simulations have come a long way, still there is a (albeit reducing) gap between the ground testing and flight. One example is the first flight of F-16, which ended in disaster because the simulator didn't accurately portray the control stick forces. Modifications are also required due to other reasons- user inputs, for example; As any changes have to be tested, it takes time. – aeroalias Jun 3 '16 at 9:08
• Was that F-16 flight using the pressure sensitive stick or had they already scrapped that idea? – TomMcW Jun 4 '16 at 19:48
• @aeroalias the first flight of F-16, which ended in disaster Well according to wikipedia, the pilot ejected safely during that first flight. What is your definition of disaster? Just saying, many first flights end in crashes but ejection seats prevent a real disaster as far as I think of the word. Just my 2 cents. – DrZ214 Jun 5 '16 at 5:47
• @DrZ214 Sorry, I missed the word 'nearly'. Actually, the pilot actually landed the aircraft safely. The liftoff was accidental during high speed taxi trials, but the aircraft was landed safely by the pilot. Sorry about the mistake again. – aeroalias Jun 5 '16 at 6:18