Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Certification Testing Extremes  
User currently offlineDufo From Slovenia, joined May 1999, 802 posts, RR: 4
Posted (2 years 1 month 2 weeks 15 hours ago) and read 2668 times:

During flight testing for certification (and also later), aircraft are pushed beyond normal limits. For example DC8 going intentionally supersonic, on my current type Saab 340 I found that it has been test flown up to 313 knots, even though it's limited to 250 etc.

What other extremes have been achieved? Altitudes, speeds, operating from unusually short runways?


I seriously think I just creamed my pants without any influence from any outside variables.
7 replies: All unread, jump to last
 
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 1, posted (2 years 1 month 2 weeks 11 hours ago) and read 2610 times:

Quoting Dufo (Thread starter):
For example DC8 going intentionally supersonic

That wasn't actually on purpose (Md for the DC8 is below Mach 1).

Quoting Dufo (Thread starter):
What other extremes have been achieved? Altitudes, speeds, operating from unusually short runways?

Yes. In order to show that you're good to the certification limit, you actually have to go slightly past it. So all aircraft have gone higher, faster, heavier, lighter, more fwd CG, more aft CG, colder, and hotter, than they're certified for.

Tom.


User currently offlineDufo From Slovenia, joined May 1999, 802 posts, RR: 4
Reply 2, posted (2 years 1 month 2 weeks 10 hours ago) and read 2585 times:

I thought that DC8 mach1+ was intentional - this article claims so: http://www.airspacemag.com/history-o...here-Boeing-Will-Never-Try-It.html


I seriously think I just creamed my pants without any influence from any outside variables.
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 3, posted (2 years 1 month 2 weeks 10 hours ago) and read 2570 times:

Quoting Dufo (Reply 2):

I thought that DC8 mach1+ was intentional - this article claims so: http://www.airspacemag.com/history-o....html

Fascinating article, I hadn't seen that before. I agree, it claims it was intentional. I'm not sure what to think about that; there are several thing in that article that hint at absolutely atrocious test conduct practices at Douglas at the time (intentionally taking off flaps-up, intentionally blanketing the elevator, doing enough engineering to get speed tables but not enough to realize you'd lock up the stabilizer, etc.). The event, as they described it in the article, is a monumentally stupid testament to bad test design and execution.

Tom.


User currently offlineCitationJet From United States of America, joined Mar 2003, 2446 posts, RR: 3
Reply 4, posted (2 years 1 month 2 weeks 6 hours ago) and read 2503 times:

Part 25 requires a demonstrated airspeed margin of 0.07 Mach above Mmo per 14 CFR 25.335(b)(2). Mmo is the maximum operating Mach. Mmo + 0.07 = Md.


Boeing Flown: 701,702,703;717;720;721,722;731,732,733,734,735,737,738,739;741,742,743,744,747SP;752,753;762,763;772,773.
User currently offlineKELPkid From United States of America, joined Nov 2005, 6411 posts, RR: 3
Reply 5, posted (2 years 1 month 2 weeks 5 hours ago) and read 2471 times:

Does Vmca have to be demonstrated to the point where the aircraft starts to roll over? If so, that's probably where the tail chute that many prototypes have comes in handy (or at least it gives the flight crew assurance that it's there if needed    ).


Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 6, posted (2 years 1 month 2 weeks 2 hours ago) and read 2439 times:

Quoting KELPkid (Reply 5):
Does Vmca have to be demonstrated to the point where the aircraft starts to roll over?

Not to roll over, you just need to get to the point that the pilots can't arrest the yaw. Since you still have full aileron authority you generally shouldn't have too much roll (C_N_beta) if you're just above Vmca but you won't be able to control the heading. This is a tricky test because the regulator really doesn't care if you certify a Vmca above the true aerodynamic Vmca but, for performance reasons, the OEM wants Vmca to be as low as possible.

Quoting KELPkid (Reply 5):
If so, that's probably where the tail chute that many prototypes have comes in handy (or at least it gives the flight crew assurance that it's there if needed    ).

That's a spin chute; it's needed if you lose directional control for any reason. That could be Vmca tests, flutter, or any of a wide variety of lateral/directional stability tests (steady heading sideslips, rudder hardovers, stalls, etc.).

Tom.


User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 7, posted (2 years 1 month 1 week 6 days 16 hours ago) and read 2344 times:

By Testing something beyond its limit & then restricting it to some percentage below that limit,ensures a buffer that things can work within certain ranges & a bit beyond.


Think of the brighter side!
Top Of Page
Forum Index

Reply To This Topic Certification Testing Extremes
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Cat II ILS Certification - US Regionals posted Mon Mar 19 2012 09:37:39 by apodino
Training/certification Needed For ICN Pilots? posted Thu Dec 29 2011 07:36:25 by YVRFlyer
South America Flights Require Etops Certification? posted Sat Dec 3 2011 19:33:32 by Valorien
GAO Report On FAA Certification Of 787 posted Thu Nov 3 2011 21:13:12 by rwessel
A350 Engine Testing. posted Sat Oct 22 2011 06:21:00 by flyvabb
Aircraft Dispatcher Certification posted Sun Oct 2 2011 14:28:20 by chicago757
Is FAA Certification Confidential? posted Wed Aug 17 2011 07:55:24 by biggles34
High Altitude Supersonic Testing Of Gas Turbines posted Mon Aug 1 2011 17:54:53 by jetmech
Boeing Testing Laminar Flow On 787 posted Fri Jun 17 2011 03:01:51 by ferpe
Additional Flight Testing After Delivery? posted Tue Jun 14 2011 18:57:10 by notaxonrotax

Sponsor Message:
Printer friendly format