Maintenance Airframe; Maintenance Powerplant
Communication Breakdown; Confusion
Aircraft Equipment Problem Critical
Aircraft Aircraft Damaged; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Chart Or Publication; Human Factors; Manuals
This report is being written for my performing an Airworthiness Check in the morning around XA:00 AM and the FAA finding the discrepancy after the outside portion of the Ramp Inspection and walking around and looking through the aircraft; FAA Inspector X looked at the pitot tube. Inspector X stated that he thought the leading edge [of the pitot] looked 'disfigured slightly'. The other FAA Inspector; Inspector Y; said he thought it was just the lighting outside that made it look 'disfigured'. But on closer inspection we all confirmed that the leading edge [of the pitot tube] at roughly the 10 o'clock position; was very slightly flattened. Inspector Y asked Pilot X if he was getting any odd readings on the Airspeed Indicator (AI) and he replied 'No; everything was operating normally'. They [FAA] stated that; they are looking at pitot tubes more closely these days due to the problems that they are seeing in the pitot tubes on the EC-135s [helicopters] in the Northwest. Upon completion of inspecting the aircraft we returned to the [Maintenance Line] shed to continue the logbook and facility inspection. While looking through an older logbook for an Airworthiness Directive (AD) signoff; Pilot X entered the shed and expressed [that] he received a flight request and will need the logbook. Pilot X asked if; 'everything was all good with the aircraft' and we said 'yes'. After Pilot X stepped out the door and made his way to the aircraft the FAA inspectors strongly expressed to me that I should really check the tolerances to the pitot tube disfigurement. Inspector Y mentioned that we all know about the disfigurement now and in the event it is out of tolerances we could all be in trouble if you guys take a flight. I asked for some guidance from Inspector Y if he knew something that I didn't know and he replied that he can't tell me that the aircraft should not fly; although he emphasized again that I verify the tolerances. After this brief conversation with Inspector Y; I expressed to Pilot X that I needed to verify the tolerances before the aircraft should be flown. Upon making a logbook entry and researching the pitot damage and determined that there wasn't any limitations listed for damage on the pitot tube; the aircraft was grounded. The Maintenance Manual states the Bell BHT-407 MM; Chapter 95; Paragraph 22; Pitot-Static System Inspection: 1). Examine all of the lines and unions for correct tightness (Figure 95-4). 2). Visually examine all of the pitot-static tube assemblies that they are correctly attached and that there is no sign of chaffing; wear; or other damage. 3. Visually examine the pitot tube (1) each and the left and right static ports (2) each. Make sure that there is no obstruction or damage. Then; a pitot tube was immediately ordered and the FAA carried on with the inspection. Upon completion of the pitot tube replacement; Inspector X requested to be contacted. [Recommend] replacing all pitot tubes that have ANY damage.
Reporter stated he works for an air medevac Operator. There is only one pitot tube on the BHT-407 helicopter. Pitot heat is available. The Bell Maintenance Manual (M/M) Chapter 95 only says to 'observe for damage' to the pitot tube. Currently no limitations exist in the Bell-407 Manual requiring pitot tube replacement and he doesn't know if Bell Helicopter engineers will issue an Maintenance Manual revision in the future to include allowable damage specifications.Reporter stated that since no previous issues with Airspeed Indication (AI) had been reported by the flight crews; he hesitated replacing the pitot tube. But; without any damage specification to make a decision and the weekend approaching and short time for Bell engineers to respond; they decided to ground the aircraft and just replace the pitot tube. There have been discussions about acquiring a 'Go-No-Go' gage (tool) that can be inserted into the pitot tube inlet opening to quickly determine if a pitot tube inlet deformation is acceptable or not. The FAA inspectors noted that erosion of the leading edge opening of pitot tubes appear to be more of an issue on Eurocopter EC-135s helicopters than on Bell helicopters.
A Line Aircraft Maintenance Technician (AMT) explains why the single pitot tube on a Bell BHT-407 helicopter was replaced after two FAA inspectors raised concerns about a deformation noted at the pitot tube's leading edge inlet opening.