In article , Ricardo
wrote:

buff82driver wrote:
http://www.military.com/features/0,1...ESRC=dod-bz.nl

How were they able to design and bring the P-51 into production within one
year
back during WW2? Why is it so expensive and take so long now?

You didn't really just ask that question, did you?

Ah maybe b/c they did not deal with highly complex technology that has
thousands of ways of failing and a few critical failures of very tiny
parts that don't even move can cause the plane to crash into the
ground. With WWII era planes about the most complex things were the big
ol' piston engines, retractable landing gear, bomb sights...etc...today
a few whiz kids could probably develop a WWII era technology fighter
plane better than any seen in WWII. All you need is metal workers,
engine mechanics/builders, and some pretty solid aerodynamic students.
If it was so easy now then the U.S. would not make everyone else's air
force into target practice.

And having a very reliable and tested British designed engine made one
hell of a contribution...

Complex technology, etc. are not the issue here.

The real issue, the point of the debate and the article is project management
philosophy.

On one side is the old guard: "Defense acquisition experts with the watchdog
Government Accountability Office" who want the aircraft to roll off the
line fully developed. What they want, in the WWII context, is a P-51H coming
off the production line from the get-go.

On the other side is the "new" project management philosophy (actually
very old) , now called spiral development, where you get a production version
flying asap and sequentially modify it as necessary based on continuing
flight test plus service experience.

There are costs associated with both philosophies. Costs to make changes
versus costs of keeping a large engineering team twiddling their thumbs
during flight test .

Politically, spiral development is much safer. You have the aircraft flying and
you can point to your successes: much less chance of having the program
cancelled since there are aircraft in the fleet.

Sprial development was out of favor for awhile because some programs
screwed the pooch and thought they could push some critical testing off
to later production versions. It ended up biting them in the ass.

F-22 did not ustilise spiral development, and look how long it took them to
go through flight test, how much it cost the program and the taxpayers, how
many aircraft were deleted as a result, and how many times the program
was almost axed.
Overspec'ing the initial development of a product gives every nitwit an
opportunity to point fingers if things do not go perfectly. And professional
politicians are not aerospace engineers, and most don't have any technical
background at all.

Omega's P-51 question is thus answered: they did it by getting the basic
aircraft flying and in service, then making literally dozens of model and sub-
model configuration changes over the next 4 years until the war was over.

I.e. Spiral Development.

--
Harry Andreas
Engineering raconteur