N339ZBeech M35 · 1960

On August 29, 2017, about 0639 mountain standard time, a Beech M35 airplane, N339Z, was substantially damaged during a forced landing near Lake Havasu City Airport (HII), Lake Havasu City, Arizona. The private pilot received minor injuries. The airplane was registered to and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed for the cross-country flight. The flight originated from Hemet-Ryan Airport, (HMT), Hemet, California, at an unknown time and was destined for HII.

According to the pilot, he kept the airplane in a hangar at HMT, and he makes the trip between HMT and HII regularly. The pilot did not recall his exact departure fuel from HMT. He conducted the takeoff and climbout, as he always did, on the left main fuel tank. After reaching his cruise altitude of 7,500 ft, he switched to the auxiliary tanks, and later, to the right main tank. While in cruise, he also activated the two pumps to transfer fuel from the tip tanks to the main tanks. He began his letdown for HII about 30 miles out, and when he had the airport in sight, as was his habit, he switched the fuel selector to the left main tank for the landing. At that point the airplane was about 4 miles from HII, and about 2,000 ft above the airport elevation. The engine stopped producing power but continued to windmill. The pilot selected the landing gear down, advanced the mixture and propeller controls, verified that the ignition switch was set to the 'BOTH' position, and that the fuel boost pump was switched on. The engine continued to windmill, but did not start, even after the pilot pushed the engine start button.

The pilot determined that the airplane would not reach the runway, and selected an open desert area as his landing location. He switched to the right main fuel tank, but there was no change in the engine; it continued to windmill only. A short time later, the pilot switched back to the left main tank, again to no avail. While on short final to his selected off-airport site, the pilot recognized that the airplane would strike a "gully" that was approximately perpendicular to his direction of travel; he intentionally pulled up to overfly the gully, with the knowledge that the airplane would likely stall as a result. The airplane overflew the gully, and came down hard on the nose landing gear. The nose landing gear collapsed, but the airplane slid upright to a stop. The pilot shut down the airplane and exited on his own.

First responders arrived on scene shortly thereafter, and the airplane was recovered to a secure facility later that day. The recovery personnel reported that none of the fuel tanks were breached, and that the airplane had about 43 gallons of fuel on board, all of which was contained in the two main tanks. The airplane was retained at the recovery facility for detailed examination by investigators.

The pilot held a private pilot certificate with an airplane single-engine land rating. The pilot reported that he had about 400 hours total flight experience, including about 145 hours in the accident airplane make and model. The pilot reported that he had successfully completed Bonanza Pilot Proficiency Program (BPPP) training through the American Bonanza Society. His most recent Federal Aviation Administration (FAA) third-class medical certificate was issued in July 2016, and his most recent flight review was completed in February 2017.

General

The airplane was manufactured in 1960, and was equipped with a Continental Motors IO-470 series engine. The pilot purchased the airplane in September 2016. Maintenance records indicated that the engine was factory-rebuilt in August 1995, and installed in the airplane at a tachometer time of about 827 hours. The most recent annual inspection was completed in June 2017. At that time, the tachometer registered about 1,633 hours.

Fuel System

The airplane was equipped with six fuel tanks, three in each wing. These were designated as Main, Auxiliary ('Aux'), and Tip. The main tanks were bladder tanks, each with a capacity of 25 gallons, of which 22 gallons were usable. Each main tank was equipped with an internal header tank located at the aft inboard corner of the main tank. The sole fuel pickup line for each main tank was located inside each header tank. The fuel pickup line included an attached finger screen, and threaded into a fitting on the header tank. The outboard side of each header tank was equipped with a one-way flapper valve that permitted fuel to flow into, but not out of, the header tank. This header tank system was intended to prevent temporary unporting of the fuel pickup during banked flight.

The bladder-type aux tanks were each 10 gallon capacity, of which 9.5 gallons were usable. The airplane was placarded to "use auxiliary fuel in level flight only." The tip tanks were non original equipment manufacturer modifications. Each of the tip tanks was plumbed to its respective main tank, and fuel could be independently transferred from the tip tank to its respective main tank via a pilot-activated pump. The airplane was placarded to "transfer tip tank fuel in level flight only."

Each main tank fuel pickup line was plumbed directly to the fuel selector valve. The aux tank fuel lines were plumbed to a single line that was then plumbed to the fuel selector valve. The tip tanks were not plumbed to the fuel selector valve.

The fuel selector valve was mounted on a horizontal surface just outboard and forward of the pilot's seat bottom, and was actuated/set by manual rotation of its handle. The fuel selector valve had four designated settings. The selector handle setting positions were not spaced uniformly around the valve control face. Assigning 12 o'clock as the forward position, the four setting positions were: Right main (4 o'clock), Aux tanks (6 o'clock), Left Main (8 o'clock), and Off (10 o'clock).

Pilots Operating Handbook (POH) Information

The landing gear was electrically controlled and actuated, and was equipped with a manual extension system for certain failures. The landing gear could be operated independently of whether the engine was producing power. The POH did not state landing gear extension or retraction times.

The only reference to fuel tank selection in the Cruise, Descent, or Before Landing subsections of the "Normal Procedures" section of the POH was contained in the "Before Landing" checklist, which stated that the fuel selector valve should set to the "more nearly full" main tank. The POH did not address any altitude considerations for this fuel tank selection.

The "Emergency Procedures" Section of the POH contained the following checklists for relevant procedures:

The 0656 automated weather observation from Needles Airport (EED), Needles California, located about 18 miles northwest of HII, included calm wind, visibility 10 miles, few clouds at 10,000 ft, temperature 35oC, dew point 8oC, and an altimeter setting of 29.85 inches of mercury.

General

The airplane was manufactured in 1960, and was equipped with a Continental Motors IO-470 series engine. The pilot purchased the airplane in September 2016. Maintenance records indicated that the engine was factory-rebuilt in August 1995, and installed in the airplane at a tachometer time of about 827 hours. The most recent annual inspection was completed in June 2017. At that time, the tachometer registered about 1,633 hours.

Fuel System

The airplane was equipped with six fuel tanks, three in each wing. These were designated as Main, Auxiliary ('Aux'), and Tip. The main tanks were bladder tanks, each with a capacity of 25 gallons, of which 22 gallons were usable. Each main tank was equipped with an internal header tank located at the aft inboard corner of the main tank. The sole fuel pickup line for each main tank was located inside each header tank. The fuel pickup line included an attached finger screen, and threaded into a fitting on the header tank. The outboard side of each header tank was equipped with a one-way flapper valve that permitted fuel to flow into, but not out of, the header tank. This header tank system was intended to prevent temporary unporting of the fuel pickup during banked flight.

The bladder-type aux tanks were each 10 gallon capacity, of which 9.5 gallons were usable. The airplane was placarded to "use auxiliary fuel in level flight only." The tip tanks were non original equipment manufacturer modifications. Each of the tip tanks was plumbed to its respective main tank, and fuel could be independently transferred from the tip tank to its respective main tank via a pilot-activated pump. The airplane was placarded to "transfer tip tank fuel in level flight only."

Each main tank fuel pickup line was plumbed directly to the fuel selector valve. The aux tank fuel lines were plumbed to a single line that was then plumbed to the fuel selector valve. The tip tanks were not plumbed to the fuel selector valve.

The fuel selector valve was mounted on a horizontal surface just outboard and forward of the pilot's seat bottom, and was actuated/set by manual rotation of its handle. The fuel selector valve had four designated settings. The selector handle setting positions were not spaced uniformly around the valve control face. Assigning 12 o'clock as the forward position, the four setting positions were: Right main (4 o'clock), Aux tanks (6 o'clock), Left Main (8 o'clock), and Off (10 o'clock).

Pilots Operating Handbook (POH) Information

The landing gear was electrically controlled and actuated, and was equipped with a manual extension system for certain failures. The landing gear could be operated independently of whether the engine was producing power. The POH did not state landing gear extension or retraction times.

The only reference to fuel tank selection in the Cruise, Descent, or Before Landing subsections of the "Normal Procedures" section of the POH was contained in the "Before Landing" checklist, which stated that the fuel selector valve should set to the "more nearly full" main tank. The POH did not address any altitude considerations for this fuel tank selection.

The "Emergency Procedures" Section of the POH contained the following checklists for relevant procedures:

The airplane came to rest upright on open, flat desert terrain about 1 mile south-southwest of the HII runway 32 threshold. None of the fuel tanks had been breached.. According to the recovery personnel, just after the accident, the left main tank contained 23 gallons of fuel, the right main tank contained 20 gallons of fuel, and the other four tanks were empty. Each tank was equipped with a filler neck and cap assembly, and all caps were found installed.

Airframe and Engine Examination

The airplane was not examined by NTSB personnel until after it had been recovered. The wings had been unbolted and removed for transport, and except for impact-related damage, the airplane was otherwise intact. When examined, the tachometer registered about 1,674 hours.

The left main tank bladder material was slightly brittle, consistent with aging. The header tank flapper valve door moved freely, and appeared to be fully functional. The header tank bladder was cut open, revealing two layers of foam, each half the height of the tank. The top layer of foam was intact, but the lower layer of foam was deformed and wrapped/folded over on itself in the region of the finger screen, in a direction consistent with the rotation direction of the screen during installation. The foam had taken a set, consistent with it having been deformed for some undetermined but substantial duration. The finger screen was detached (broken solder joints) from the inlet/pickup line, and was trapped in the deformed foam. Although the finger screen no longer performed its function, the fuel inlet line did not appear to be obstructed.

The right main tank bladder material appeared newer and more flexible than that of the left main bladder. The header tank was opened. Unlike the left tank, it was not foam-filled, and the pickup screen was intact and attached. The flapper valve door moved freely, and appeared to be fully functional.

The fuel selector placard was worn to the point where the position marker for the left tank was absent. The fuel selector valve detents were less than positive/firm, consistent with wear, and there was moderate resistance in handle rotation. The handle was able to be rotated continuously in either direction. The valve port dimensions were such that a handle rotation arc of about 25° (about 1/16 of a full 360° rotation) would transition any port between fully open and fully closed. This arc equates to about 3/8 to 1/2 inch of travel of the selector handle end. According to FAA publication AC43-13-1B paragraph 8-34d, an "improper fuel valve position setting can seriously reduce engine power by restricting the available fuel flow. Check [the mechanism] for wear and excessive clearance which prevent the valve from positioning accurately."

The engine-driven fuel pump (EDP) connection of the fuel line from the selector valve to the EDP was observed to have utilized Teflon tape on the male fitting that threaded into the EDP; the use of Teflon tape for this connection is prohibited, per FAA AC43-13-1B, paragraph 8-38f. Functional tests using low pressure shop air revealed that all fuel lines were properly routed and clear, and that the fuel selector functioned properly in all four positions. Subsequent disassembly of the fuel selector valve revealed that its design limited handle rotation to about 180o, through all 4 positions, but that the internal mechanism limiting handle rotation had failed, which permitted the handle to be rotated continuously in either direction. The failure did not appear to affect valve functionality.

The electric fuel boost pump was located in the left wing wheel well. The pump was observed to be installed securely, with secure fittings and no evidence of any damage or fuel leakage. The pump was removed from the wing and tested via the application of 12vdc. The motor operated, and fuel was ejected from the outlet side of the pump.

Visual examination of the engine indicated that it appeared to be intact. All cylinders were undamaged, and securely installed on their cylinder bays. The top spark plugs were removed and visually inspected; they displayed normal operating and wear signatures when compared to published guidance by Champion. Borescope examination of the upper chambers of the cylinders revealed that the cylinder bores, valve heads, and piston faces displayed normal operating and combustion signatures. The crankshaft was rotated manually, and continuity was established between the crankshaft, camshaft, connecting rods, and the associated components driven by the accessory gears on the aft face of the engine. During crankshaft rotation all cylinders displayed thumb compression and suction

During manual crankshaft rotation, both magneto impulse couplings operated normally, and both magnetos produced sparks. The EDP remained attached to its installation point and was undamaged, and all fuel lines remained secured to the EDP. The throttle and metering assembly remained attached to its installation point and was undamaged. The throttle and mixture control arms remained secured to their shafts, and the control cable rod ends remained secured to the control arms. All fuel lines were secure. The fuel manifold valve remained attached to its installation point and was undamaged. There were no signs of fuel leaks or any other anomalies noted. The induction system displayed minor impact damage to the induction Y-pipe. The exhaust system remained attached to the engine and displayed minor impact damage. There were no signs of induction or exhaust leaks noted.

The two blade, variable pitch propeller remained attached to the crankshaft. Both blades remained attached to the propeller hub and displayed impact damage. One blade displayed aft bending deformation and scratches in multiple directions on the propeller face, with chordwise scratches at the propeller tip. The other blade displayed minor aft bending deformation and chordwise scratches at the propeller blade tip.

Engine Test Run

Based on the examination results, the engine was removed from the airframe and shipped, without the propeller, to Continental Motors in Mobile for a test run attempt. The rear two mount legs were fractured. Some blue/green staining was noted on the engine oil sump. The magneto-to-engine timing for both magnetos was found to be set 1o earlier than the manufacturer's specified value. The engine was placed on a stand, and some baffling and accessories were removed for the test run The engine was prepared for operation by installing the appropriate thermocouples, pressure lines, and test pads for monitoring purposes.

The engine started normally on the first attempt without hesitation or stumbling in observed rpm. The rpm was advanced in steps for warm-up in preparation for full power operation. The engine throttle was advanced to each of four different rpm values (1,200, 1,600, 2,450 and full) and held at that rpm for five minutes to stabilize. At each setting, the engine performed normally without any hesitation, stumbling, or interruption in power. The throttle was then rapidly advanced from idle to full throttle five times, and again the engine performed normally. Throughout the test phase, the engine accelerated and performed normally, and demonstrated the ability to produce rated horsepower.

Restarting Fuel Injected Engines

Chapter 6 (Aircraft Systems) of the FAA publication Pilot's Handbook of Aeronautical Knowledge (PHAK) stated that running a fuel tank dry will cause the engine to stop, and that "running a tank completely dry may allow air to enter the fuel system and cause vapor lock, which makes it difficult to restart the engine. On fuel-injected engines, the fuel becomes so hot it vaporizes in the fuel line, not allowing fuel to reach the cylinders."