However, during the last few days, there have been two situations discovered, along
with new information about an earlier fatal accident. In our view these are matters about
which every owner of the FliteCraft/Turbo2000 systems_ would wish to be promptly informed.
Without waiting for further investigation, and without waiting for the _FAA to_ complete its review of these matters, and without regard to any other consideration, we are taking the initiative to promptly provide you with this_ information and to provide_ you our recommendations as to what should be done,_ now.
Data from the following three Bonanzas are of immediate concern:
One: On Wednesday,_ November 18, a Bonanza with a 1994 turbonormalizing system suffered the inflight_ loss of the tailpipe._ This is the "S" shaped 3.5" diameter stainless steel_welded tubing part that attaches to the exit from the turbocharger turbine housing flange.
This tailpipe is attached to the turbocharger flange with an aerospace quality_ stainless steel bolted "V-band" clamp, which is in widespread use in general aviation exhaust applications.
First reports, from a mechanic who has seen this specific part, are that there appears to be an old crack in the clamp which had ultimately failed.__ We have only cursory information on the age or number of hours of in-service use_ of the installed_ "V-band" clamp, but the information available suggests that it was in service for some time. It may, and we emphasize "may", have_ been recently removed and reinstalled.
The loss of the tailpipe resulted in some smoke in the cockpit. The pilot_ reduced power to idle and did an excellent job of making a successful landing at a nearby airport._ There is significant heat damage to portions of the engine compartment_ adjacent to the turbo case, but it appears to be repairable.
Two: By coincidence, also on November 18,_ the owner of a turbonormalized Bonanza,_ with approximately 1100 hours in service, had the airplane in the shop for a_ routine annual inspection._ During the inspection, it was discovered that the_ same "V-band" clamp at the junction of the turbo case housing and the tailpipe had failed._ The part had apparently been failed for some time, as there was evidence of significant chafing and wear at the adjacent and attached slip joint on the wastegate bypass exhaust tubing.
Three:In June of 1998,__ a turbonormalized Bonanza suffered an accident with two fatalities._ The preliminary NTSB report did not suggest that the turbo housing flange/tailpipe "V-band" clamp was in any way associated with the cause of that accident. Information that we received during the last week suggests that there was a crack or hole in the turbocharger case. The information further suggested that the associated "V-band" clamp was broken, although there is no information suggesting that the exhaust pipe was missing. At present, because of the unusual finding of the cracked turbocharger case housing, it appears the cause of this accident may be related to that problem. However, pending further investigation, we have no way of knowing for sure whether or not this accident is related to the first two maintenance items, or not._ However, we wanted to make sure you are as fully informed as possible at this time.
We offer the following as our opinion of this situation, along with our recommendations:
WHAT WE THINK:
There are over 200 of the FliteCraft and Turbo2000 aircraft flying since the_ STC was first approved over 10 years ago._ These aircraft have accumulated tens of thousands of successful, reliable, operating hours. The exhaust system in these aircraft has a reputation among mechanics knowledgeable about the system as_ being more durable and more reliable than any other turbocharged exhaust system_ installed in any general aviation aircraft. Some of these individual aircraft_ have thousands of hours on the original exhaust system without any significant_ problem.
Thus, based on the description of the two recent problems that we now have_ available to us, it appears that this problem is most likely maintenance related, and does not involve any fundamental defect in the design or the materials._ The new information about the fatal accident in June of 1998, is also, obviously of concern, even if the particular circumstances and cause of that accident yet remain unresolved.
WHAT WE RECOMMEND:
BEFORE FURTHER FLIGHT: We recommend and urge that, before further flight, the "V-band" clamp which attaches the tail pipe to the turbocharger should be inspected visually in accordance with the attached Mandatory Service Bulletin, (MSB) TAT 98-1.
If the visual inspection reveals no discrepancy, then the aircraft may be returned to service subject to the new 400 hour/ 4 year service life limit described in MSB TAT 98-1.
Otherwise, the aircraft should be grounded until the clamp can be replaced with a new
or serviceable clamp.
AT NOT MORE THAN 25 HOUR INTERVALS:
At not more than 25 hour intervals, and while the engine is cold, the pilot/owner/operator of one of these turbonormalized systems should_ simply grasp (with one hand) the cold tailpipe that extends from the left lower cowl flap area, and give the part a firm_ push/pull from side to side.
If the tailpipe appears in any way to be loose, or_ insecure, the aircraft should be grounded until an A&P with IA can remove and_ inspect the tailpipe and the associated V-band clamp, in accordance with the_ suggested inspection and reinstallation instructions described in the attached MSB, TAT 98-1.
AT 100 HOUR INTERVALS: The existing "Turbo-Flite 520/550 System Maintenance and Trouble Shooting Manual" calls for periodic 100 hour removal of the exhaust pipe and its associated "V-band" clamp in order to facilitate the inspection of the turbine impeller. At that inspection, particular attention should be paid to the condition of the "V-band" clamp and to the proper nut torque during re-installation.
IT IS CRITICALLY IMPORTANT THAT ALL RESULTS OF THE INSPECTION BE REPORTED,
REGARDLESS OF THE OUTCOME, SO THAT WE CAN ACCUMULATE A DATABASE OF THE RESULTS, TO BE USED
AS A BASIS_ FOR ANY FURTHER RECOMMENDATIONS THAT MIGHT BE APPROPRIATE.
A SUGGESTED FORM FOR THE REPORTING OF THE RESULTS OF THESE INSPECTIONS IS ENCLOSED WITH
We have ordered a small supply of approved replacement "V-band" clamps.__ While they last,_ we will supply these parts to any person who returns to us the_ old part, for our inspection.__ At present, we anticipate the cost, with two day_ shipping and handling, to be approximately $45.00.
We regret that our first communication with each of you has come under these_ circumstances._ It is our intention to try provide expeditious service information concerning any of the old parts and_ components, as well as prompt information concerning any_ future parts or components as such information becomes available to us.
We have no idea what action, if any,_ the FAA may take with respect to_ the information described in this letter.__ However, we believe these matters warrant prompt attention.
Tim Roehl George W. Braly
President Chief Engineer
Tornado Alley Turbo, Inc.