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X-Air Ultralight Aircraft Re: Indicated airspeed problem

 

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Guys the Official figures are
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Xair Vne is 83kn
Xair Falcon Vne is 85kn
Xair Hawk Vne is 125mph
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These are figures the aircraft was tested to and cannot be increased without further load testing,
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The reason some of you may have different figures eg in the aircrafts MAAN is during that aircraft initial flight test those are the figures the test pilot set to suit that aircraft and the calibration of its instruments.
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If an aircraft has a MAAN placard of 90kn then that is due to the fact the aircraft ASI is over reading, before any Vne run in a check flight the check pilot should first confirm the accuracy of the ASI system.
Also these will differ with aircraft fitted with ASI in mph or Knots
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This issue all stems back to the early years of the Xair when we told the BMAA the pitot static system at the wing that they wanted dosnt read correctly, open static at rear of dash (doors must be fitted) or static tube just poked up inside of wing strut gives a far more accurate ASI reading.
After doing the first flights in about 50 new Xairs and falcons I have seen what works.
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But I would not panic about flying your aircraft over the Vne, due to the drag of the aircraft it is in fact fairly difficult to get a standard 582 Xair to do a true Vne run.
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Seamus
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----- Original Message -----
Sent: Friday, July 27, 2018 9:25 AM
Subject: X-Air Ultralight Aircraft Re: Indicated airspeed problem

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This is all well and good, however if the aircraft has been changed since it was built it could be that the MAAN figures used by the BMMA are incorrect and they could potentially be asking members to fly their aircraft significantly over VNE.
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I solved the problems with my own aircraft and got my permit. I took advice from various experts and then flew the VNE test again.
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Before re-flying the the VNE test, I made a rough calibration myself to check that I was not doing anything dangerous. I simply flew level at full throttle into wind and then full throttle down wind and observed the GPS speed and IAS.
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The GPS speed was approximately in line with my expectations and so I did the test. I actually did the VNE test twice, again into and down wind. ( there was little wind on that day ) During the test I kept an eye on the GPS speed and ensured that it never at any time exceeded 95 knots.
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Which is 10 knots faster than VNE and also the maximum speed achieved by the test pilot during certification of the the aircraft. By coincidence, my particular aircraft was the prototype used in the original testing and so I know it has flown at 95 knots previously.
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I am very concerned that other owners may be persuaded to fly their aircraft at dangerous speeds and I have heard stories of X airs being pushed to a near vertical dive to achieve the required indicated airspeed.
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To me that suggests they may well have been flying too fast. Mine achieved VNE with a steep dive on full throttle, it was not vertical or anything near it. I simply opened the throttle fully and when maximum level speed was achieved, I pushed the nose down and allowed the aircraft to accelerate to VNE.
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Aside from the these particular concerns, more generally I don’t see the point of any test where the only two possible outcomes are either a pass or a fatal accident.
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Regards,
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Jon

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