Boeing B17 — Windsor Locks, CT

What happened

The National Transportation Safety Board (NTSB) identified the following safety issues during this accident investigation:

the need for an appropriate regulatory framework for living flight history experience (LHFE) flights, including maintenance and management policies and procedures;

the need for increased Federal Aviation Administration (FAA) oversight of LHFE operations; and

the need for FAA oversight of LHFE operators’ safety management systems (SMS).

These safety issues are discussed in the NTSB’s aviation investigation report addressing broader systemic safety issues associated with revenue passenger-carrying operations currently conducted under Title 14 Code of Federal Regulations Part 91, including LHFE flights. That aviation investigation report, titled Enhance Safety of Revenue PassengerCarrying Operations Conducted Under Title 14 Code of Federal Regulations Part 91 (NTSB/AAR-21/03), can be accessed from the Aviation Accident Reports page of the NTSB’s website. This report includes references to safety recommendations from the Part 91 aviation investigation report.

The vintage, former US military bomber airplane was on a tour that allowed members of the public to purchase an excursion aboard the airplane for an LHFE flight. The accident flight was the airplane’s first flight of the day. During the initial climb, one of the pilots retracted the landing gear, and the crew chief/flight engineer (referred to as the loadmaster) left the cockpit to inform the passengers that they could leave their seats and walk around the airplane.

One of the pilots reported to air traffic control that the airplane needed to return to the airport because of a rough magneto. At that time, the airplane was at an altitude of about 600 ft above ground level (agl) on the right crosswind leg of the airport traffic pattern for runway 6. The approach controller asked the pilot if he needed any assistance, to which the pilot replied, “negative.”

When the loadmaster returned to the cockpit, he realized that the airplane was no longer climbing, and the pilot, realizing the same, instructed the copilot to extend the landing gear, which he did. The loadmaster left the cockpit to instruct the passengers to return to their seats and fasten their seat belts. When the loadmaster returned again to the cockpit, the pilot stated that the No. 4 engine was losing power; the pilot then shut down that engine and feathered the propeller without any further coordination or discussion.

When the airplane was at an altitude of about 400 ft agl, it was on a midfield right downwind leg for runway 6. Witness video showed that the landing gear had already been extended by that time, even though the airplane still had about 2.7 nautical miles to fly in the traffic pattern before reaching the runway 6 threshold.

During final approach, the airplane struck the runway 6 approach lights in a right-wing-down attitude about 1,000 ft before the runway and then contacted the ground about 500 ft before the runway. After landing short of the runway, the airplane traveled onto the right edge of the runway threshold and continued to veer to the right. The airplane collided with vehicles and a deicing fluid tank before coming to rest upright about 940 ft to the right of the runway. A postcrash fire ensued.

Postaccident examination of the airframe revealed no preimpact mechanical anomalies that would have precluded normal operation. Teardown examination of the Nos. 3 and 4 propellers revealed that their blades were in the low-pitch and feathered positions, respectively.

Teardown examination of the No. 4 engine revealed that the left magneto’s P-lead was partially pulled out of the magneto housing and that a single strand of safety wire was around the retaining nut. Although the No. 4 engine’s left magneto produced a strong spark on the ignition leads for all nine cylinders, the grounding tab contacted the housing and caused the magneto to short and not function during a postaccident test. The No. 4 engine’s right magneto produced no spark on one of the nine ignition leads and a weak and intermittent spark on the other eight ignition leads because of wear to the compensator cam. The shortedout left magneto would have caused rough engine operation and a partial loss of engine power that would have been exacerbated by the weak right magneto, which is likely what prompted the pilot to shut down the No. 4 engine and return to the airport.

With the No. 4 engine shut down, the pilot would have had to use a higher power setting for the No. 3 engine to compensate for the loss of power from the No. 4 engine. Teardown examination of the No. 3 engine revealed evidence of detonation on four of the nine cylinders. In addition, the teardown examination revealed that the spark plugs were worn and had gaps between the electrodes that were beyond the manufacturer’s specifications. The condition of the spark plugs likely resulted in detonation and a partial loss of engine power that further reduced the total thrust available and exacerbated the thrust asymmetry. The pilot likely did not recognize, or recognized too late, the extent of the loss of engine power on the airplane’s right side.

The pilot had performed a preflight run-up check of the magnetos at an engine speed of 1,700 rpm, which was higher than the 1,600-rpm speed in the Collings Foundation’s run-up checklist; after the check, the magnetos appeared to perform normally. However, a B-17 engine ground test checklist included instructions to check the magnetos at an engine speed between 1,900 and 2,000 rpm. If the pilots had been required to perform the magneto check at the higher rpm, they might have detected the detonation on the No. 3 engine and/or the magneto anomalies on the No. 4 engine (if either resulted in an rpm drop that exceeded 100 rpm, which would have been inconsistent with the B17’s acceptable limits) and taken action before the flight to resolve the issues.

During the return to the airport, the pilot flew the traffic pattern at an airspeed of 100 mph and below, and he allowed the airspeed to decay far below that required to minimize the loss of altitude over a given distance flown (about 120 mph). It is likely that the airplane was unable to maintain altitude at the lower airspeeds because the pilot could apply only a limited amount of power to the left-wing engines while simultaneously trimming the asymmetric thrust with the available rudder authority. Extending the landing gear created additional drag that exacerbated this situation; the landing gear should not have been extended until it became evident that the airplane could reach the runway. If the pilot had lowered the airplane’s nose to maintain the airspeed that was initially achieved during the climb and kept the landing gear retracted until landing on the runway was assured, the NTSB’s airplane performance study showed that the airplane could likely have overflown the approach lights and touched down beyond the runway threshold. Thus, the pilot did not appropriately manage the airplane’s configuration and airspeed after he shut down the No. 4 engine.

The accident pilot was also the Collings Foundation’s director of maintenance and was responsible for performing the airplane’s maintenance while it was on tour. However, the teardown examinations of the Nos. 3 and 4 engines revealed maintenance issues that were not addressed during the airplane’s current tour. For example, the No. 3 engine’s 25-hour inspection occurred less than 1 month before the accident. As part of that inspection, the spark plugs should either have been cleaned, inspected, and tested or replaced with new plugs, and the gap between the electrodes should have been checked. The teardown examination found worn spark plugs with gaps between the electrodes that were beyond the manufacturer’s specifications, which should have been identified and corrected during the inspection of the No. 3 engine. As previously stated, the worn spark plugs would have contributed to the partial loss of power on the No. 3 engine and the asymmetric thrust.

The 25-hour inspection also includes a check of the point gap for each magneto. The No. 4 engine had its 25-hour inspection 9 days before the accident, but the teardown examination found that the gap between the points on the right magneto was less than the minimum gap that the manufacturer required, indicating that this check was either not performed or was improperly performed. As a result of the point gap, most of the ignition leads produced sparks that were weak or intermittent, adding to the loss of engine power caused by the short in the left magneto. To address the aircraft maintenance deficiencies found in this and other accident investigations discussed in the Part 91 aviation investigation report, the NTSB issued Safety Recommendation A-21-9 in April 2021. This safety recommendation asked the FAA to “develop national safety standards, or equivalent regulations, for revenue passenger-carrying operations that are currently conducted under Title 14 Code of Federal Regulations Part 91, including, but not limited to…living history flight experience and other vintage aircraft flights.” The recommendation stated that these standards, or equivalent regulations, should include (among other things) operationally specific maintenance requirements.

At the time of the accident, the Collings Foundation was operating with an LHFE exemption that provided the operator with relief from specific FAA regulations. The FAA’s most recent letter granting the Collings Foundation’s exemption stated that the foundation “must maintain and apply on a continuous basis its safety and risk management program that meets or exceeds the criteria specified in the FAA [LHFE] Policy.” The FAA’s policy stated that LHFE operators, including the Collings Foundation, were required to have a plan to mitigate risks that followed safety risk management principles.

The Collings Foundation implemented an SMS about 2 1/2 years before the accident, which could have met the requirements of the FAA’s LHFE policy and the FAA’s letter that granted the foundation’s LHFE exemption. However, the SMS was not an effective safety risk management program. The SMS safety officer, who was responsible for managing the SMS, was a part-time, volunteer pilot and, as such, interacted with the foundation’s management and personnel on a sporadic basis only. Further, the SMS did not detect and appropriately manage the risks associated with safety issues related to the pilot’s inadequate maintenance of the airplane while it was on tour.

The SMS also did not detect that the Collings Foundation’s engine run-up checklist was inconsistent with the B-17 engine ground test checklist or that the pilot and copilot did not wear their shoulder harnesses during flights (as reported by the loadmaster). In addition, the SMS did not detect that the loadmaster’s passenger briefings might have been insufficient (as indicated by statements from multiple surviving passengers that the briefing did not include information about seat belts, exits, or emergency equipment) or that he would stand unrestrained between the pilot and copilot during takeoff and landing, even though the foundation indicated that the seat to the left of the ball turret was available for him. The pilots’ failure to use their shoulder harnesses and the loadmaster’s failure to be restrained during takeoff and landing were inconsistent with federal regulations addressing the use of safety belts and shoulder harnesses.

Even though the Collings Foundation was not specifically required to have an SMS, the FAA’s most recent letter granting the Collings Foundation’s exemption stated that the foundation was required to have an SMS manual (used as a basis for an equivalent level of safety) and provide it to the Orlando, Florida, Flight Standards District Office (FSDO). However, the manual was not a regulatory or an approved document, and the FSDO did not review the manual or the safety reports submitted as part of the SMS to ensure that the SMS met or exceeded the safety risk management criteria in the FAA’s policy for operators with LHFE exemptions. As a result, the FAA’s oversight of the Collings Foundation’s SMS was not effective in identifying and mitigating safety risks. In April 2021, the NTSB issued Safety Recommendations A-21-13, which asked the FAA to require SMS for the revenue passenger-carrying operations discussed in the Part 91 aviation investigation report; these operations included LHFE flights. The NTSB also issued Safety Recommendation A21-14, which asked the FAA to provide ongoing oversight of each operator’s SMS once established.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.