The weekly rollerboard 19 January: A350 special

The A350XWB flight test campaign continues in earnest, and with more than 850 flight hours now logged it’s time I wrote an update. I was following the campaign and the CSeries more closely in the initial stages, but the number of great resources available online meant I took a bit of back seat.

Flexible limits

The static test frame MSN5000 has now successfully completed ultimate wing load testing reaching a five metre deflection the wing, subjecting the wing to loads to 1.5 times greater than expected in service life. Strains were measured by 10,000 measurement channels which correlate load information against structural design models.

The ultimate load is the beyond which the wing is expected to fail, and is calculated at 2.5 times the maximum expected G load. As the Airbus Fly By Wire system limits G loads to +2.5G or +3.5G in a reversion to Direct Law, the ultimate load could be higher than 7.5G.

For the first time Airbus didn’t stress the wing to its load failure point – the moment at which the wing breaks. Composites shatter rather than break in an unpredictable way as the fibrous matrix carries multiple load paths; unlike comparable metal wings if both wings failed and were then analysed there would be no common characteristics between the two that indicated tension load was the cause of the failure. Also, as composites shatter they release needle-sharp fibres presenting a challenging cleanup. So the actual failure load may never be known.

High as a kite.

The second test A350 MSN3 has completed completed high altitude testing at the Bolivian airports Cochabamba (8,300 ft AMSL) and La Paz (13,300ft AMSL).

Operations at this altitude are particularly straining on the aircrafts engines, APU and environmental control systems. Test flights assessed takeoff and landing performance, as well as engine and handling performance during simulated engine failures events on takeoff. In addition, the flights validated autopilot performance at high altitude, oxygen systems and avionics ventilation.

A350 MSN2 landing at La Paz. Click the image for more amazing photos by estebaneid on flickr of the A350 in Bolivia.

ETOPS extremes

Airbus is seeking regulatory approval for ETOPS  (Extended Twin Engine Operations or Engines Turn Or Passengers Swim) 420 operations, which would allow the A350 to fly up to seven hours from an aerodrome on one engine.

Currently the 777 with GE engines has ETOPS 330 approval, the A330 ETOPS 240, while the the Boeing 787 remains restricted to ETOPS 180.

There is no trans-polar or oceanic route in the northern hemisphere that requires more than ETOPS 240 approval, so Airbus’ application for  ETOPS 420 would only open up new possibilities down south. The only practical application of 420 minute ETOPS would for polar operations over Antarctica, and that really only opens up a handful of routes. Of these only one – Auckland to Johannesburg – has commercial imperative the others all rely substantially on hub traffic. That commercial imperative may change over the next 20 years, and while there is jet capable runways in Antarctica, it’s unlikely the CASA or the FAA would approve operations so far from fields that could not support emergency landing requirements.

Perhaps, Airbus is just looking for bragging rights through endorsement of the A350, or is it an attempt to lift and govern the standards of future aircraft design?

Paper aeroplanes

I’ve got some pretty cool models at home, but this is genuinely incredible. Luca Iaconi-Stewart, an architecture student and #avgeek, has built a 1:60 scale model of an Air India 777-300ER made entirely of manila folders. But there’s a level of fastidiousness that goes further than just gluing together some paper together. Iaconi-Stewart’s model incorporates functional doors, latching mechanisms, a full retraceable landing gear, thrust reversers all built with hands and tweezers. For parents looking to teach their kids how to make a paper aeroplane, the bar has just been lifted a notch.

*updated 19 January to correct mistaken reference to A350 static test frame as MSN500 rather than MSN5000.

3 Responses to The weekly rollerboard 19 January: A350 special

  1. Couple of points, since Im one of the lucky ones who is a part of the A350 full scale static test camlaign in TLS:

    - static airframe is MSN5000 (not MSN500)

    - at the moment it is still intended to break the wings and perhaps fuselage as well (a decision may change).

    An aircraft certification requires that a test article sustains 1.5 x limit load. This was proved by this test campaign – ultimate load tests. After these residual strength tests are planned which are not required for the certification. Even during the A380 static test campaign the wings were not intended to fail below 1.5 x limit load; however it happened; they did not sustained ultimate load.

    • Thanks for commenting, apologies for the mistaken airframe reference I’ve now updated the post. Pretty amazing that you are part of the test campaign. I’m aware of the 1.5x limit load required for certification of any aircraft, are you able to provide some more info on residual strength testing? I assume it’s an assessment of the level of changes or warping in the composite carbon fibre matrix?

      Hope you enjoy the blog.

      Jeremy

      • Full scale tests, as mentioned in your article, are performed to validate the numerical models and verify design principles. Therefore, in such tests the material behaviour is not investigated. This is studied by a large number of lower-level tests within the test pyramid (coupon tests, element tests, etc…).

        One of the key answers that you can get from the residual strength testing (static load up to rupture) is the real strength of the wing and fuselage which may be important in the future optimisation / weight reduction of the aircraft. The residual strength (damage tolerance) is primarily a fatigue-related topic. The A350 full scale fatigue is tested by three separate fuselage sections + wing.

        Keep up with the good job, I enjoy reading your articles.

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