Ultralight Aircraft Airworthiness Notice
5
ABN 40 070 931 645
PO Box 1265 3/1 Pirie Street,
FYSHWICK ACT 2609 Fyshwick ACT 2609
Phone: (02) 6280 4700
Fax: (02) 6280 4775 E-mail:
5 March 2002 (as amended 31 Jan 2005)
ULTRALIGHT AIRCRAFT AIRWORTHINESS NOTICE
IDENTIFICATION NUMBER – 95/6 Issue 5
WING STRUT CARRY THROUGH STRUCTURE
To: All Owners and Operators of all Models of Skyfox and Gazelle Aircraft.
Introduction.
This AN re-issue – 96/6 Issue 5:
· supersedes AN 95/6 Issue 4 which called for inspections and servicing of the lift strut carry through tube in the fuselage of Skyfox and Gazelle Aircraft.
· mandates a safety back up to the lift strut carry through tube pending a terminating action by offering a backup tube as a low cost and easy to instal solution. Continuing inspections of the lift strut carry through tube in the fuselage of Skyfox and Gazelle Aircraft remain but at much extended intervals.
Background:
A third report has been reported verbally advising of a crack in the lift strut load carry through tube of a Skyfox aircraft. Full details of this third incident are not available at the time of writing, but the fact that a third incident has occurred reinforces the need for finalising airworthiness action.
The first incident was an in-flight failure in which the sideways loads imposed by the lift struts was taken by the lower fuselage longerons passing the load to other structural members as well as to the seatbelts in the aircraft. The thought of the lift loads splaying the fuselage longerons apart is a frightening structural condition.
The second case was discovered during inspection of a CA 22A/25aircraft at 2598 hrs TiS. The aircraft concerned was fitted with a CAR 35 approved external reinforcement which is similar to the scheme being mandated by this issue – Issue 5 – of Airworthiness Notice 95-6. This reinforcement may well have prevented a catastrophic failure, but it did not prevent the onset of cracking in the basic fuselage cross-tube. The Reporter stated that the crack in this instance “occurred quite suddenly” implying that although the area was being routinely inspected and it had developed over a very short period of flying. The reporter stated that the fuselage of this aircraft had been powder coated after extensive repair following a major accident and that the paint may have hidden the crack until it had become large enough to affect the paint.
These reports confirm that fatigue failure in the basic fuselage cross-tube is likely in these aircraft, especially those having the light-wall cross-tube. Note that all Skyfox and the first 3 Gazelle aircraft were manufactured with this lift strut carry through member in the bottom of the fuselage manufactured from tube with a wall thickness of .035 inch, while the member in Gazelles Serial Numbers 4 and onwards had a wall thickness of .058 inch. There have been no reports of problems with the thicker wall tubes to date.
Consequently, urgent action is necessary to strengthen the lift strut carry though structure.
The simplest and most economic means to ensure airworthiness integrity is considered to be the installation of a back up member in the same load path as the integral fuselage structural member. This back up member is basically another simple tube (of the heavier .058 inch wall thickness) that attaches at the structural “clusters” (joints) where the lift struts attach to the aircraft. This new member attaches with the same bolts as the lift struts so expensive processes such as welding are avoided. Depending on how it is installed and on other factors, It may not necessarily share the load fully with an undamaged fuselage tube, but it will provide a load path which is stronger than the original should a failure in the original occur.
The Back-Up Member introduced by this AN is CAR 35 Approved and at least one CASA approved Organisation can supply them at about $300 or a little more per item. It is simple and within the capabilities of a Level 2 to instal.
This action does not constitute terminating action – although it may well be. Continuing inspection of the area is still considered necessary – but at a vastly increased time interval.
Terminating action is being addressed by CASA and CAR 35 Engineers.
ACTION REQUIRED:
All models of Skyfox/Gazelle aircraft are to be subject to the following requirements:
Requirement 1: Log Book Check – Before Next Flight
Requirement 2: Dye Penetrant Inspection – Before Next Flight unless carried out within the last 100 Hrs
Requirement 3: Install Back up Tube – within 100 hrs or by 31 July whichever occurs first
Requirement 4. Continuing Inspections – Visual and Dye Penetrant
Requirement 5. Every Two Years Check Oil in the Fuselage Tube.
Requirement 1. BEFORE NEXT FLIGHT
Inspect the aircraft log book. Inspect the aircraft log book for the entry/entries certifying compliance with AN 95/6 Skyfox Issue 4 Requirements 1, 2 and 3.
Note that AN 95/6 Skyfox Issue 3x required initial action before 1 May 2002 and that the 2 yearly check of oil levels required by Requirement 3B should now have been carried out and recorded as one two yearly interval would have already arisen.
Requirement 2. BEFORE NEXT FLIGHT
Dye Penetrant Inspection. Unless the inspection specified by AN 95/6 Issue 3x Requirement 2 or AN 95/6 Issue 4 Requirement 2 has already been performed and certified in the aircraft log book within the last 100 hours, aircraft having more than 1000 hrs TiS are to be inspected as described in A and B below before next flight
A. Gain access to the wing lift strut mount cross tube structure inboard of the lower lift strut attachments. Remove the paint from the wing lift strut mount cross tube, using a non abrasive method, in the area shown in Figure 1 on page 3.
Note: Gaining access to the wing lift strut mount cross tube for inspection in accordance with Requirement 3 may require cutting a hole in the fabric covering. A hole 50 mm in diameter should be sufficient.
B. using a dye penetrant method, inspect the wing lift strut mount cross tube inboard of the strut attachment lugs for signs of cracks at both the port and the starboard fittings. Pay particular attention to the inboard end of the strut attachment lug weld as indicated in Figure 1 below. If any cracking or other anomaly is found, the aircraft is not to be flown until the cross tube member is replaced (see “Additional Information” below on page 4) and refilled with oil as per Requirement 5. Repaint the cross tube lightly (not thick enough for paint to seal a leak or mask visual identification of a crack) before returning the aircraft to service.
FIGURE 1
Requirement 3: Within the Next 100 Hours Time in Service or by 31 July 2005 whichever occurs First
Install Fuselage Underside Lift-Strut Backup Tube or other CAR 35 Approved Scheme to ensure continuing airworthiness integrity of the lift strut carry through structure.
One such approved scheme is fitment of the
Southdown Engineering Order 25-EO-06 Issue 2, 24 Jan 2005 Lift Strut Carry Through Structure Reinforcement Tube (Marked with Part Number 25EO06)
produced by B&R Aviation in Toowoomba
(Phone 07 4634 1706 - Email )
installed in accordance with the
Southdown Engineering Order 25-EO-07 14 January 2005 - Instal lower fuselage lift-strut carry-through backup tube.
(Copy will be provided with the item, P/N 25EO06 on purchase)
Note 1. The Southdown Engineering Scheme is offered as an approved and economic scheme which can be installed by a Level 2.
Note 2. Other schemes approved by a CAR 35 Authority, with hardware produced by a CASA approved organisation and installed by a Level 2 or appropriate CASA LAME are acceptable. For continuing airworthiness management purposes, copies of any such schemes when fitted to an aircraft are to be forwarded to Recreational Aviation Australia for retention together with the Serial Number and Registration Number of the aircraft to which they have been applied.
Note 3. Election to comply with CASA Airworthiness Directive AD/CA21/5, AD/CA25/2 (as applicable) and any follow up directives performed by an appropriate Level 2 or CASA LAME is an acceptable means of compliance with this Airworthiness Notice. However, having elected this as the Means, all existing and future CASA requirements relevant to the lift strut structure and load path are to be followed in entirety. “Cherry Picking” (selective incorporation of parts that may appear more expedient) between the CASA and Recreational Aviation Australia schemes is not permitted. For airworthiness management purposes, the Serial Number and Registration Number of any aircraft being maintained to the CASA requirements/ADs are to be forwarded to Recreational Aviation Australia.
Requirement 4: Continuing Inspections.
A. Before incorporation of the structural integrity measure introduced by Requirement 3 (within the next 100 hours or until 31 July whichever occurs first).
Visual Inspection – at each 10 Hours for Skyfox & Gazelle S/N 1,2 & 3
At each 25 Hours for Gazelle S/N 4 & Onwards
Inspect both sides of the wing strut carry through tube and adjacent fabric. A sketch of the typical area is in Figure 1 above. Inspect for cracks, evidence of fluid seepage from the tube or for any corrosion damage. The cause of any fluid seepage is to be determined and rectified and any cracks and corrosion are to be repaired before returning the aircraft to service.
This requirement is superseded by “B” below following incorporation of Requirement 3.
B. After Incorporation of Requirement 3
Visual Inspection – All types
After the first 50 hours following incorporation of requirement 3 and then at each 50 hours inspect both sides of the wing strut carry through tube, the reinforcing tube and adjacent fabric for cracks, evidence of fluid seepage from the tube or for any corrosion damage.. (Note that the reinforcing tube P/N 25EO06 is oil filled so it should be monitored for leakage also). A sketch of the typical area is in Figure 1 above.
The cause of any fluid seepage is to be determined and rectified and any cracks and corrosion are to be repaired before returning the aircraft to service.
Dye Penetrant Inspection as per Requirement 2.
- Skyfox & Gazelle S/N 1,2 & 3. At each 250 Hours from incorporation of Requirement 3
- Gazelle S/N 4 & Onwards. At each 500 Hours from incorporation of Requirement 3
Requirement 5. Every Two Years Check Oil.
Remove the 3/32" blind type sealing rivet from the wing strut carry through tube oiling hole. Check that corrosion preventive fluid is present in the tube, using a small diameter wire as a dipstick. Refill the tube with up to 100 ml of Shell ENSIS fluid, or similar corrosion preventive fluid. Refit a 3/32" blind type sealing rivet in the oiling hole.
Note: Skyfox Aviation Service Bulletin No 10 also refers to oiling of the wing strut carry through tube. Addition of a colour contrast dye to the preventive fluid may assist inspection with Requirement 3. Check before use to ensure the dye has no adverse effects on either the corrosion inhibitor properties of the fluid or on the tube material.
Additional Information: If cracking is found, the affected tube is to be removed and replaced by a new item having 0.058 inch wall thickness before next flight. All such repairs must be approved under CAR 35.
This does not constitute terminating action for the problem: however terminating action is being addressed by CASA and CAR 35 Engineers and will be subject of further advice. It is quite possible that this may be the finalising requirement, although ideally an integral structural modification such as a retrofit replacement of the problem tube with a redesigned item would be a typical industry solution. However, this is probably not warranted as a mandatory requirement for the recreational fleet.
Recording:
Compliance with each requirement is to be recorded in the aircraft log book against AN 95/6 Issue 5.
Reports Required:
1. Findings of any cracking, corrosion or other anomalies in the area are to be reported to Recreational Aviation Australia immediately by defect report.
2. Serial and Registration Numbers of aircraft which comply under Requirement 3 Notes 2 and 3 (ie those that will not incorporate the Southdown EOs 06 and 07) are to be advised to Recreational Aviation Australia for airworthiness management purposes.
Technical Manager
Defect Reporting is one of the primary ways we have in ensuring continued safety in our operations.