Accident Analysis: Single-pilot versus Two-pilot - Is There a Safety Advantage?

Jun 5, 2015 - 10:00 AM

AIN analysis comparing accidents involving one-pilot versus two-pilot business jet operations from 1977 through 2014 reveals, somewhat surprisingly, that from a statistics standpoint there is only a slight safety advantage to having a multiple cockpit crew in this class of airplane. The analysis examined 107 accidents, 40 (or 37 percent) of which were in jets piloted by a one-pilot crew versus 67 accidents (63 percent) in jets crewed by two pilots. Although there were more two-pilot accidents, half of the single-pilot accidents were fatal crashes compared with 45 percent of two-pilot accidents. Details of the findings in this article start with the first and heavily reported fatal accident involving a business jet flown by one pilot.

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  • Accidents by Type
  • Accidents by Model

On Aug. 2, 1979, the fatal crash of Citation 501 N15NY would likely have been reported as just another tragic accident involving a private jet, except that the pilot killed was New York Yankees catcher Thurman Munson. He had played for the team for 11 years before his death at the age of 32 at the controls of his newly acquired twinjet. As expected, media coverage was expansive, often sensationalistic and usually technically challenged. But one aspect of the story the lay press missed reporting, or didn’t understand the significance of, was the fact that the crash was the first fatal accident involving the newly FAA-approved certifications of airmen and certain light jets for single-pilot operations. 

Munson’s newly purchased aircraft crashed and burned when it stalled short of the runway while attempting to land after completing several touch-and-goes. The two passengers escaped from the wreckage with serious injuries. The NTSB determined the accident was caused by the pilot’s “failure to recognize the need for and to take action to maintain sufficient airspeed to prevent a stall into the ground during an attempted landing.” The pilot also didn’t “recognize the need for timely and sufficient power application to prevent the stall during an approach conducted inadvertently without flaps extended.” Contributing factors were the pilot’s “failure to use the appropriate checklist and his nonstandard pattern procedures, which resulted in an abnormal [high and fast] approach profile.”

Some news stories and industry chatter speculated that the pilot was neither experienced enough nor properly qualified. The NTSB reported that FlightSafety International in Wichita conducted the ground, simulator and flight training for Munson’s rating. The flight training consisted of 10 flights (six cross-country and four local) for a total of 21.7 hours and 24 landings. On July 17, Munson obtained his type rating on a 1.5-hour flight that included eight landings. His total pilot time at the time of receiving the type rating was 505.6 hours. His total landings in all types of aircraft (primarily with propellers) were approximately 688.

In the 16 days following the type-rating check, Munson flew 10.6 hours. He logged his total time of 4.1 hours as single-pilot PIC of the Citation 501 during this period. This time was accumulated on flights from Akron to Columbus, Ohio, and back on July 26; to Chicago on July 29; and the return flight to Akron in the early morning hours of August 2. Both passengers were rated pilots but had not flown in jets before this ride. The passenger in the right seat was a flight instructor who had trained Munson for his instrument rating.

According to the NTSB, Munson had not used a checklist on the approach previous to the accident but had extended the gear and flaps just before turning base. On the accident approach he pulled the power back to or about idle on an extended downwind to reduce airspeed and altitude. When the gear warning horn sounded, “he shut the horn off” manually. Neither passenger started to become apprehensive about the approach until beginning the turn onto final. At this time, the passenger in the right seat–by looking at the red VASI display–was aware that they were below the glide path and descending while still some 4,000 feet to 5,000 feet from the runway threshold. In addition he knew the gear was not down and made a comment to that effect to Munson, who immediately lowered the gear, further increasing the sink rate. No flaps were extended during this approach.

This accident, and dozens that follow, raises the question of whether single-pilot jet operations are inherently less safe than two-pilot missions. No one can say for certain that this accident could have been avoided if there had been a qualified pilot in the right seat. Nor did the Safety Board allude to that possibility. What’s more, AIN’s study of virtually all one-pilot accidents compared with two-pilot accidents in jets approved for one-pilot operations from 1979 through 2014 lacks conclusive evidence–in our opinion–to make a case either way because the statistics show similar numbers as a percentage of accidents, as well as in the types of accident involving both single-pilot and two-pilot flights. 

Distinction without a Difference?

Of the 107 worldwide accidents with business jets eligible to be approved for single-pilot (SP) flights, 67 were flown by two qualified pilots (TP) at the time of their mishaps. Single-pilot flights accounted for the remainder. Additionally, those accidents, both SP and TP, represent a small portion of the approximately 4,000 jets that were built by the end of last year that were eligible for FAA approval for one or two pilots. They are the Cessna Citation 500/501, Citation 510 Mustang, Citation 525, Hawker Premier, Eclipse 500, and Embraer Phenom 100 and Phenom 300. 

Perhaps more telling is a comparison of fatal crashes and fatalities. Twenty, or 50 percent of the single-pilot accidents, killed 58 people. Thirty, or about 45 percent of the two-pilot accidents, resulted in 102 fatalities. While these figures show that the percentages of fatal accidents for one- and two-pilot crew are close, more people perished in two-pilot accidents in the 37 years since 1977 when the FAA began certifying specific jets and airmen for single-pilot operations. On average, single-pilot flights had fewer people on board than the aircraft flown by two pilots.

The most common type of accident was a runway excursion on landing–38 incidents, or nearly 36 percent of the total–a percentage that holds true for the type of accident on average incurred by the entire business jet fleet. Most runway excursion accidents or incidents were survivable and, depending on the extent of aircraft damage, some were not even officially reportable to the NTSB. Excursions with far more serious results typically happened when a cockpit crew decided to abort the landing and attempted a go-around with insufficient runway remaining. Notably, our study revealed that TP ops experienced 26 excursions, more than double the 12 for SP landings. Two-pilot ops suffered five go-around accidents versus two for SP ops.

In addition to the Munson accident, there are several other mishaps in which it could be argued that a qualified airman in the right seat might have made a difference in the outcome. For example, a sole pilot flying his U.S.-registered Citation 525 in the UK got into trouble when he apparently got distracted from monitoring the aircraft while using an iPad. According to the UK incident report, as the jet approached its cruising altitude of FL430, the IAS decreased to about 128 knots. The pilot then reduced the rate of climb to 500 fpm. However, over the next 50 seconds, the speed decayed by a further 10 knots. Close to FL430, “the pilot checked his tablet to check the forecast.” At that moment the aircraft pitched severely nose-down and rolled to the right, departing from controlled flight in a series of five 360-degree rolls to the right. The pilot briefly regained control before the aircraft stalled again, and the ensuing recovery overloaded and structurally damaged the aircraft’s wings.

Investigations into several fatal SP accidents also might raise the question "Could they have been prevented if operated with two pilots?" At the same time, there are a number of two-pilot accidents in SP-eligible jets for which investigators also placed the probable cause on the pilot, with the exception of a disastrous runway collision.

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  • Single-pilot Accidents
  • Two-pilot crashes

Most Non-N Aircraft Are Flown TP

Of the 107 total accidents AIN examined, 43 involved non-U.S.-registered airplanes, of which just four occurred under single-pilot command. All but one were fatal. But of the 39 accidents involving non-U.S.-registered jets flown by two pilots, four were fatal. One of the nonfatal single-pilot accidents involving a non-U.S.-registered aircraft was an unintentional gear-up landing in a Citation I/SP.

Another SP accident in a non-N-numbered Citation 525 occurred in the U.S. and was more serious. The NTSB final report says the pilot performed “a low pass” over the runway at Atlantic City Bader Field and then, with a tailwind of about 10 knots, touched down approximately 1,000 feet beyond the approach end of the 2,948-foot-long runway. After touchdown, the airplane continued off the end of the runway and came to rest in the water. The aircraft not only landed long and with a tailwind, but the pilot apparently ignored a notation on the published airport diagram for Bader that read “airport closed to jet aircraft,” according to the Board. The diagram was “found attached to the pilot’s control column” after the accident. The same notation was posted in the FAA Airport/Facility Directory.

As a percentage of total single-pilot eligible models in the fleet, the number of accidents closely reflected the number in the fleet. Therefore, it was not surprising to find that the Citation 500/501/525, with more than 2,600 manufactured, had the most accidents. The Citation 500 was the non-N-numbered model involved in by far the most accidents.

It wasn’t until November 2012 - a full 35 years after jets started gaining approval for single-pilot operation - that an FAA rule took effect that requires single-pilot jet operators to meet basically the same Part 61.58 yearly checks as two-pilot operators had been required to meet for many years previously. Before that mandate, single-pilot jet operators were required to meet essentially the same biennial flight review required of non-jet operators. However, despite the relatively new requirement, there are no marked changes in the ratio of SP versus TP accidents over the last two years, according to AIN’s analysis.

While the emphasis of this article has been on accidents befalling jets flown by one qualified pilot, the data shows that these same models of business jet flown by two qualified pilots experienced nearly an equal share of accidents, many of them under similar circumstances and with the same fatal results. That’s clearly evident when looking at the charts accompanying this article. Certainly, many corporate flight departments perceive having two qualified pilots on passenger flights as providing a higher level of safety than having just one pilot up front. In any case, even if the accident statistics did not support this perception, many flight departments limit their SP missions to maintenance or ferry flights. Take a look at the data presented here, and then you make the call.