Jet One Express CVLP at San Juan on Mar 15th 2012, engine trouble

Last Update: December 2, 2014 / 16:28:49 GMT/Zulu time

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Incident Facts

Date of incident
Mar 15, 2012

Classification
Crash

Cause
Engine trouble

Aircraft Type
CONVAIR CV-440 Metropolitan

ICAO Type Designator
CVLP

On Dec 2nd 2014 the NTSB released their final report concluding the probable cause of the crash was:

The National Transportation Safety Board determines that the probable cause of this accident was the flight crew’s failure to maintain adequate airspeed after shutting down the right engine due to an in-flight fire in one of the right augmentors. The failure to maintain airspeed resulted in either an aerodynamic stall or a loss of directional control.

The captain (65, ATPL, 22,586 hours total, about 9000 hours on type) was pilot flying, the first officer (44, CPL, 2,716 hours total, about 700 hours on type) was pilot monitoring. Prior to departure the crew performed a run up of both engines for about 15-20 minutes, ground personnel and crew did not notice anything abnormal with the engines during the run up. The crew subsequently received departure instructions to follow the standard eastern departure route for visual flights. The crew requested a second engine run up, typical for the aircraft, which was conducted on taxiway C while holding short of B. The aircraft subsequently taxied to runway 10 and departed.

97 seconds after becoming airborne the first officer declared emergency, the captain requested a left turn to return to San Juan and asked whether ATC could see any smoke off the aircraft, ATC confirmed the transmission but did not verify any smoke - the NTSB reports in a foot note, that the air traffic controller did not notice any more smoke from the engines than usual, although he radioed "uh, the engine is smoking" this was meant as acknowledgement of the pilot's transmission.

An airport official driving a truck around the aerodrome and familiar with the aircraft reported he did not hear any unusual sounds or notice anything unusual when the aircraft departed. Ground surveillance cameras at the aerodrome also did not record any indications of smoke or fire as the aircraft climbed over the end of runway 10. A witness in an apartment complex about 1 mile east of the aerodrome and just south of the extended runway center line reported however that he heard strange noises that he described as intermittent engine surges, he saw the aircraft lose altitude and turn north.

Radar data indicated that the aircraft continued to climb, the speed over ground remained between 140 and 160 knots, the captain advised they needed to land on runway 28, air traffic control cleared the aircraft to land on runway 28. The aircraft reached a maximum altitude of 935 feet MSL while in a left hand turn (30 degrees bank angle) to return to the airport. 205 seconds after becoming airborne, while descending through 500 feet MSL, the aircraft began rolling right at a speed of about 140 knots over ground, 248 seconds after becoming airborne radar contact with the aircraft was lost at 110 feet MSL and at an estimated speed of 88 knots over ground, 278 seconds after becoming airborne the aircraft impacted Laguna La Torrecilla.

The NTSB reported that the aircraft carried a load of bread, according to invoice 12,100 lbs of cargo. The estimated ramp weight of the aircraft was 47,710 lbs with a maximum allowable takeoff weight of 40,900 lbs.

The NTSB reported that the captain was required to undergo a competency check every year. It could be established that the captain had received a competentency check on Jun 24th 2010 valid until Jun 30th 2011, however, the general manager of Fresh Air, also known as Jet One Express, who was also the son of the captain and was responsible to maintain pilot records, was unable to provide evidence that the captain had undergone a competency check in the last 12 months before the accident.

The NTSB reported that the captain had witnessed an inflight engine fire on another Convair on Jan 17th 2011. While overflying that other aircraft he noticed the fire and radioed the crew, that they had a fire and needed to turn around, the crew made it back (the NTSB quoted the captain's son: "by the skin of their teeth"). The NTSB reported with respect to this other accident: "Postaccident examination of the airplane’s left engine revealed a discrepancy in two cylinders in which the pistons did not move during rotation of the engine. This discrepancy may have resulted in unburned fuel or oil entering the exhaust system and igniting in the exhaust or augmentor assemblies. Although the augmentor assemblies were not available for examination, the location of the fire suggests that there was a leak in the vicinity of the augmentor assemblies and muffler junction, causing the fire to burn inside the nacelle rather than exit out the aft end of the muffler."

The NTSB reported that the minimum control speed for the aircraft is 87 knots and the published stall speed for level flight was 97 knots. The NTSB added: "However, minimum control speeds increase substantially for a turn into the operative engine, as the accident crew did in the final seconds of flight. As a result, the airplane was operating close to both stall and controllability limits when radar contact was lost."

The NTSB reported that the left hand engine controls were found in positions fully consistent with the engine operating at takeoff power, the right hand engine's thrust lever however was found in the closed position, the throttle valve was in a position consistent with the engine being shut down. A post accident examination of both engines did not reveal any mechanical failure that would have prevented normal operation of the engines, neither engine or exhaust manifolds showed indications of thermal distress or fire.

The post accident examination found the left hand propeller in the fully feathered position, while the right hand propeller was found in a position consistent with takeoff power setting.

The NTSB reported that according to testimony by other flight crew of the company the autofeather system on the accident aircraft was not operative, it's circuit breaker had been pulled. In addition, the captain usually had the autofeather system turned off even when operative. It was similiar with the aircraft's antidetonation injection system (ADI), the captain had the habit of not arming the system even if operative. The NTSB analysed, that with both systems operative and armed, the maximum allowable takeoff weight would have been 48,000 lbs, with the autofeather inoperative/not armed the maximum allowable takeoff weight reduced to 43,500 lbs and with both autofeather and ADI systems inoperative/not armed the maximum allowable takeoff weight was 40,900 lbs and stated: "The NTSB concludes that based on the captain’s history of ADI and autofeather nonuse and the postaccident position of the autofeather switch, the flight crew likely did not use the ADI and autofeather systems during the takeoff; as a result, the accident airplane exceeded the maximum allowable takeoff weight of 40,900 lbs."

With respect to the left hand propeller found feathered instead of the right hand propeller, the NTSB analysed: "Pilots flying multiengine aircraft are generally trained to shut down the engine experiencing a problem and feather that propeller; thus, the flight crew likely intended to shut down the right engine by bringing the mixture control lever to the IDLE CUTOFF position and feathering the right propeller, as called out in the Engine Fire In Flight checklist. This would have left the flight crew with the left engine operative to return to the airport. However, postaccident examinations revealed that the left propeller was found feathered at impact, with the left engine settings consistent with the engine at takeoff or climb setting. The right engine settings were generally consistent with the engine being shut down; however, the right propeller’s pitch was consistent with a high rotation/takeoff power setting. Had the autofeather system been ARMED, the right propeller would have automatically started the feathering process and, simultaneously, a blocking relay would be energized, preventing the left propeller from feathering. Because the autofeather system was not activated, the flight crew had to manually feather the propeller and likely manually selected the left propeller to feather at some point before impact with the water."

The NTSB analysed that the aircraft did not carry a flight data or cockpit voice recorder, it was not required to be equipped with these recorders. The investigation thus was unable to determine when the crew shut the right hand engine down and when the left hand propeller was feathered. However, as the aircraft continued to climb initially at an airspeed above the single engine climb speed until the controller cleared the aircraft to land back, it was thus likely that the right hand engine had not been shut down until the aircraft became cleared to land. The NTSB continued: "The radar data then indicate a relatively steady decline in altitude until the final right turn to align with runway 28. The calculated airspeed on the accident flight was around 140 knots when the airplane began to bank to the right to line up with runway 28, but then decreased during the right turn. The NTSB concludes that although the flight crew feathered the left propeller at some point during the return to the airport, the feathering likely occurred late in the accident sequence because the flight profile indicates that at least one engine was generating thrust until near the end of the flight."

The NTSB reported: "Airframe fire and thermal damage were found on the airplane’s right wing rear spar, nacelle aft of the power section, and in the vicinity of the junction between the augmentor assemblies and the exhaust muffler assembly. Damage to the airframe extended from the right engine firewall aft to the flaps, with the damage greater on the outboard side compared to the inboard side. The rear spar was intact with several areas of significant fire damage. Sooting was present on all of the rear spar aft surfaces, and the spar web exhibited evidence of burn-through in three areas concentrated toward the right side. The lower bulkhead that forms the aft end of the right wheel well remained attached, with several areas exhibiting heat damage. The right inboard flap had some melting and other heat-related signatures on the upper surface on the forward outboard corner, and sooting was present on the top surface of the flap; the inboard flap was otherwise intact. The inboard end of the right outboard flap exhibited fire damage, including a section of the attached flap track, as well as a section of the inboard edge that was missing and presumed destroyed in the fire. Damage to the remaining inboard portion of the right outboard flap extended about 14 in along the trailing edge and 28 in along the leading edge."

The NTSB analysed: "All of the fire and thermal damage was located aft of the engine and the fire detection/warning system installed on the airplane. Additionally, the condition of the paint on the upper right wing skin within the nacelle area was consistent with long-term exposure to high heat exceeding normal operation. The paint discoloration and lack of oil residue on the right augmentors when compared to the left augmentors and when compared with augmentors from an exemplar airplane indicated that the right side was exposed to much higher temperatures than the left side. While the investigation could not determine the exact location of the ignition source, it appears to have been aft of the engine in the vicinity of the junction between the augmentor assemblies and exhaust muffler assembly. Statements from mechanics familiar with this type of airplane indicate exhaust fires do occur in the augmentors on this type of aircraft. Under normal conditions, the fire is exhausted out the muffler assembly, resulting in little or no damage to the aircraft. A fire leaking out of the augmentor assembly at the junction with the muffler assembly would have produced the damage that was found on the accident aircraft. Although the source of fuel for the fire could not be determined, oil or fuel leaks into the exhaust system are capable of igniting in the presence of the high heat within the augmentors and would have led to the exhaust fire. Thus, the NTSB concludes that the thermal damage to the airplane resulted from the ignition of a flammable liquid in one of the right augmentors, and a leak in the vicinity of the augmentor/muffler junction allowed the fire to exit the junction and damage portions of the right wing."

The NTSB analysed, supported by testimony of the captain's son, that the captain was pilot flying initially, the first officer made the initial emergency call consistent with the usual distribution of the captain flying the outbound (heavy) leg carrying cargo and the first officer doing the (light) return leg (without cargo). However, all later communication was done by the captain suggesting that the first officer became pilot flying during the emergency while the captain worked the checklists and assumed pilot monitoring duties.
Incident Facts

Date of incident
Mar 15, 2012

Classification
Crash

Cause
Engine trouble

Aircraft Type
CONVAIR CV-440 Metropolitan

ICAO Type Designator
CVLP

This article is published under license from Avherald.com. © of text by Avherald.com.
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