LAA issues mod pack for grounded Zenair CH 601 XL - Sept 2009
In October 2008 the CAA issued an MPD (Mandatory Permit Directive) which grounded the popular CH601 XL, due to concerns over structural integrity of the wing attachments and possible aileron flutter. The LAA has just released a modification to the wing attachments, adds aileron mass balances, alters the elevator trim system and weight and cg range. Incorporating this modification allows individual CH601 XL aircraft to be cleared once more for flight. “
The LAA modification package can be downloaded here
The flight test report can be downloaded here
The flutter flight test report can be downloaded here
A discussion of the flutter test results can be downloaded here
Francis Donaldson
Chief Engineer
1st September 2009
Zenair flight test successfully underway - July 2009
Following the grounding of the Zenair CH 601 XL by a CAA MPD, LAA Engineering have now completed the first phase of the instrumentated flight testing to prove the effectiveness of the new aileron mass balances developed to prevent aileron flutter. Following modifications by LAA Inspector Gary Johnson, Zenair CH 601 XL G-EXLL, owned by LAA Member Neil Grantham, has been successfully flight tested to Vne. These tests have been conducted at various aileron cable tensions and the instrumentation is showing excellent damping of the wing vibratory responses even at cable tensions well below the manufacturers recommended settings.
Weather permitting, and barring snags with the remaining tests, it should be possible to complete the flight test program before the end of July. The results of these tests will then need to be analyzed in detail in a report written for the CAA, recommending the various modifications incorporated, which all being well would lead to the modified aircraft (and any others in the fleet modified in the same way) being un-grounded.
Francis Donaldson
20th July 2009
Permission to test fly Zenair CH 601 XL Granted by UK CAA
Following a briefing meeting at Gatwick with the CAA flutter and structures experts, the CAA has now given permission for the LAA to start the flight program on a modified Zenair CH601 XL fitted with aileron mass balances and wing attachment reinforcements. This permission temporarily exempts the aircraft from the MPD which currently grounds the type, so that the effectiveness of the modifications can be explored. LAA Engineering are now awaiting the arrival of the test equipment which has been specified to record the behaviour of the airframe during the flutter testing. Once the equipment is installed and wired up, flight tests will explore the ASI calibration, flutter behaviour, cg range, pitch stability and the sensitivity of the elevator trim tab. The flight testing will take place from a farm strip near Cambridge.
Emergency MPDs issued
The last few weeks has proved a busy time for the Civil Aviation Authority’s Safety Regulation Group having produced two Mandatory Permit Directives (MPD’s), both requiring ‘urgent’ inspections of gyroplanes. The first MPD concerns the RAF 2000 type, in the news recently over the approval of a mod to incorporate a tailplane to improve longitudinal stability. This MPD requires the inspection of the rudder cables and can be downloaded here.
The second MPD relates to cracking problems in the structure of VPM M14 and VPM M16 Tandem Trainer Gyroplanes and requires a full inspection of the airframe. This MPD can be downloaded here.
More Mogas Problems Reported
We’ve had three reports of Mogas having deleterious effects on fuel system components over the last week, we’re investigating these issues of course and will let members know what we find. Put the fuel system on the pre-flight check list ……. the last thing that a pilot needs is a serious airborne fuel leak …… if you find anything unusual, let us know at LAA Engineering.
Regular readers of Safety Spot, the LAA magazine’s regular continuing airworthiness feature, will already be aware of all these issues. If you haven’t seen Safety Spot before, take a look; you can download copies from the LAA website, just click on ENGINEERING and go to Safety Spot, it’s worth a visit! Or better still, if you’re not an LAA member and therefore don’t get the mag, call HQ to sign up – you know it makes sense.