A flight instructor reports that during touch and go's their Cessna 182T aircraft began running rough after lift-off. The Lycoming engine indications showed two cylinder EGT's off-scale low. Questions about fuel not used by plugged injectors actually creating an overly rich mixture for remaining cylinders; have not been answered.
Synopsis
A flight instructor reports that during touch and go's their Cessna 182T aircraft began running rough after lift-off. The Lycoming engine indications showed two cylinder EGT's off-scale low. Questions about fuel not used by plugged injectors actually creating an overly rich mixture for remaining cylinders; have not been answered.
Narrative
I was Instructor providing familiarization training to a fully qualified pilot (he was PIC) on new Turbo Cessna 182. Aircraft had just finished 50-hour break-in period and this was first flight with reduced power settings and training maneuvers (Touch and Go's etc.). During first portion of flight [we] experimented with different power settings to verify performance with Pilot Operating Handbook performance section. Aircraft engine ran smooth; except during leaning when slight roughness noted. This was thought to be normal engine roughness due to overleaning of engine. When mixture was advanced slightly roughness ended.Approaching the traffic pattern for landing practice; the engine operated normally at a lean power setting. On base turn the Mixture was enriched and prop control set full forward; approach and landing normal. During the power-up for the touch and go; all appeared normal at first. As aircraft lifted-off and passing 30 FT AGL; the engine began running rough. Distance left on runway was too short to abort takeoff; terrain at end of runway not suitable for landing (buildings; rocks; trees). Aircraft slowly accelerated to approximately 70 KTS. I (Instructor); took control of the aircraft from the PIC who was flying. I began a coordinated 15-20 degree bank for a 270 turn back to airport. Aircraft was slowly accelerated to max Lift/Drag (L/D) (78-82 KTS); max altitude obtained estimated at 150 AGL. After 270 degree turn aircraft was set up for a tight 90 degree turn to final for a successful landing. During the time period of the event (20-30 seconds); the majority of time was spent surveying for least damaging landing spots in the event of further loss of power. A momentary glance at engine Multi-Functional Display (MFD) indications showed two cylinder EGT's off-scale low. Other EGT's were midscale (normal to slightly low). No other inflight analysis was done. A ground witness later reported he heard the very rough running engine and noticed black smoke from the aircraft. After landing the aircraft was shut down and towed to hangar. [Engine] cowl was removed and no apparent engine damage or oil leaks noticed. Initial discussion with [licensed] Airframe/Powerplant (A/P) and Inspection Authorized (I/A) Technician indicated a probable fuel injector problem. That initial conclusion seems reasonable based on off-scale low EGT readings and observed black smoke.I believe this aircraft's Fuel Control is set to deliver a computer determined fuel flow based on Manifold Pressure (MP); RPM; and Mixture setting. If one or more injectors are plugged then the total fuel commanded is still delivered but it is delivered to fewer remaining operating cylinders. This produces an overly rich mixture in the remaining operating cylinders. The aircraft has been impounded [by me] and further Maintenance Inspections are to be performed next week. My follow-up will include determining if one or more fuel injectors were plugged; and if injectors were plugged; why are they plugged?
NASA callback
Reporter stated he was basically the Check Pilot operating as an Instructor. He and the PIC have airline experience. He was at full power with 34 inches of Manifold Pressure at 2;400 RPMs; pushing 26 gallons of fuel per hour and still had difficulty getting enough torque for the prop. The ground witness who heard the engine running rough thought they had crashed because he saw the black smoke from their Cessna 182T just as the aircraft disappeared below the rocky skyline.Reporter stated although the organization he volunteers to fly for is government funded; they operate as a Part 91 for most of the time. Maintenance of their aircraft is provided by a private Maintenance Organization with a five year non-cancelable contract that has Maintenance Providers at different locations. He impounded the Cessna 182T aircraft as the Safety Officer; in order to determine cause of the engine roughness and loss of power. After initiating discussions with the Maintenance Provider at his location; he was informed that new procedures from the private Maintenance Organization headquarters stated that pilots are not permitted to talk with the local Maintenance providers; but must go through the company's central office. Reporter stated he knows the tanks were sumped and were considered clean. But the fuel filter was not replaced and no inspection of the filter seems to have been accomplished. Rubber O-rings for the fuel injectors were replaced; but no reference or information whether or not the O-rings had deteriorated and contributed or caused some injectors to be plugged. The sign-off in the Logbook only noted that the injectors had been cleaned and reinstalled. No information indicating if contamination of any of the injectors was found.Reporter stated he recommended that since the aircraft and the Lycoming engine were still under warranty; with only fifty flight hours when the engine problems occurred; that Lycoming do the investigation of the problem; or at least be part of the review. But the Maintenance organization headquarters did not seem interested. He did manage to talk with a Representative of the engine manufacturer who sent Maintenance procedures; not Service Bulletins about the engine. Reporter stated the engine technical Representative seemed to agree that if some injectors were plugged that the metered fuel that was not used by the plugged injectors; would in fact be pushed into the remaining operating injectors; causing a rich mix. But he; (Reporter); doesn't have any hard data to support those comments. He believes the same type of incidence could occur again; and without any real effort at investigating the loss of power and whether or not the excess fuel mixture from the fuel manifold into the operating injectors creates another problem is unknown.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.