VFT(virtual flight testing)

[Jeremy85]

Is there some regulations for VFT? I think it is the trend of flight test techniques developing. what is your opinion?

[Zoom-56]

If there is a generally accepted definition of VFT, I'm not sure what it is. (Computational Fluid Dynamics? Real-Time Computer modeling? In-Flight Simulation? Scale modeling? Integrated multi-aircraft scenario development? With pilots in sims? Computer vs computer?) The list goes on. How about offering a couple examples of what you are referring to?

[Jeremy85]

Sorry to reply Zoom-56 late because of the vocation. According to "VIRTUAL FLIGHT TEST AS ADVANCED STEP IN AIRCRAFT DEVELOPMENT" written by Edmund Baltes and Wilfried Spitz (EADS Deutschland GmbH), VFT was defined as ＾the performance of selected flight test tasks according to operational aspects on representative ground test facilities such as flight simulator, system integration rigs, test benches and flight test ground station￣. I think it just likes the intergration of what you listed. The groud facilities and test task are used to reduce the testing effort on developing aircraft. To achieve the aim, the groud facilities should be build to represent the real aircraft and flight enviroment as closely as possible. I can't find any regulations of criterions for this. I have no idea that which level of the groud facility is fine for the certification and what tests i do in the ground facility should be acceptable by the FAA or EASA.

[Pilotage]

The short answer is probably "none".

The use of ground simulation is part of the shortening and de-risking of airborne testing. Ultimately, it's still the airborne test data which is used for certification.

P

[ICT_SLB]

Jeremy,
Was waiting for the clarification. Contrary to Pilotage's reply, the answer in North America is "yes". Provided the rigs & test facilities you use are correctly configured to a traceable standard (and this is a very big proviso) you can use those test results for certification. In some cases, such as proving the logic for a warning is correct, it is much better (and safer) to do this on an EICAS test rig than on the aircraft.

The process is not in the regs as such but has been enshrined in SAE ARP 4754, which tries to ensure the original system requirements are met by marrying each one with a test result or other engineering finding - essentially the same as the Design Compliance Report but over both the equipment vendors and airframer.

[Jeremy85]

Thanks for Pilotage and ICT_STB.
Yes to ICT_STB. The aim of VHF is some different with the shortening and de-risking of airborne testing through training the flight crew in the flight simulator to get high flight skills or be familiar with the risk avoiding procedure. VFT can substitute to a certain percentage the real test flights by reducing the number of test points to be verified by actual flight trials about "10%-30%". Making assumption, 10 test points should be verified in actual flight test in tradition, but now we can use 7 test points in actual flight to verify the flight quality and to assure the accuracy of the "flight simulator" and use 3 test points in "flight simulator" to verify the flight quality.
I want to quote the issue of "VIRTUAL FLIGHT TEST AS ADVANCED STEP IN AIRCRAFT DEVELOPMENT"
"It was the objective of the experts who have created VFT to make this method part of the verification procedure of military aircraft and qualification. Therefore the national airworthiness authority had to be involved in this process and at the end they had to endorse VFT as formal step in aircraft certification.
The following qualification aspects had to be fulfilled in order to get an official approval. First, the overall amount of verification and certification effort must be compliant with contractual requirements of the aircraft development. Second, corner points of block clearance envelope have to be confirmed by real flights. Third, additional safety margins to flight limitations must be applied until results from VFT were verified by real flights. And fourth, flight safety considerations shall not be corrupted by relying purely on VFT results.��---AIAA 2002-5823
The authority will be involed in the VHF, but it is difficult to prove the quality and accuracy of the VFT results is enough to support the certification.So the criterion should be established first, the VHF can be developed better and better.
It will be a big proviso, but it will be become more important in the future flight test. So i think it is a good topic to research.

[Shawn Coyle]

It's been going on for years. Part of the way to make sure flight tests are successful is to simulate first, then test and then update the simulation on the basis of the flight tests.
Especially important for integrated avionics.

[Jeremy85]

It's true. Are there some successful applications in some Aircrafts?

[ICT_SLB]

Jeremy,
As Shawn said, it has been in use in a limited way for some time especially for Avionics (see the sticky about SITS testing). Only recently has the concept been expanded to cover all aspects of testing and, much more to the point, had buy-in from the certification authorities. I'm not so sure, for commercial transports at least, if you could get away with not flight testing a particular configuration - it's a requirement for AFCS under AC25-1329.
A certain Canadian manufacturer is currently using ARP 4754 for its latest transport - how "successful" this will be remains to be seen.