Just a Reminder
Unless absolutely necessary, it is best to not touch any levers or switches after landing until the airplane is clear of the active runway and can safely be brought to a full stop. That goes triple for retracts. This appeared in the August 25 ASIAS report: BEECH 35 AIRCRAFT LANDED DESTINATION AND PILOT RETRACTED GEAR DURING ROLL OUT, TAYLOR, TX. Aug. 24, 2023.
Personal Minimums
If you have followed my safety work over the years, you have seen that I firmly believe in establishing our personal minimums well in advance of any planned flight. The FAA has put together a new and rather comprehensive article on the subject. Their publication includes information on the relatively new weather cameras plus numerous other important links. Check it out here.
Wake Turbulence Revisited
Wake turbulence has been a popular topic to write about in the past, but lately we do not hear very much about it. Unfortunately, my unscientific analysis of accidents appears to show that the number of accidents and incidents involving wake turbulence is on the rise. The mishaps involving the wake turbulence or rotor wash generated by a helicopter seem to be more prevalent. this month's blog, "Wake Turbulence Revisited" provides a fresh look at this hazard. Accompanying that, we have Episode 11 of "Old Pilot Tips" focusing on the wake and rotor wash issues created by helicopters and a YouTube video with the same title as the blog, "Wake Turbulence Revisited."
Wake Turbulence Revisited
We all learned about the dangers of wake turbulence and about avoidance techniques during our initial training. The FAA written exams always included at least one question on the subject.
Imagine approaching an air carrier airport on a nice VFR day in a single-engine GA airplane when the tower controller broadcasts, “Follow the Boeing 737 on a two-mile final. Cleared to land. Caution, wake turbulence.” In most cases, our training kicks in and we visualize those diagrams showing why we must not cross the path of the arriving airliner and what we must do to remain clear of the danger.
But there appears to be a slight, but alarming increase in accidents and incidents caused by wake encounters with other than large airplanes. Most legacy wake turbulence training focuses on the risk of a small airplane getting mixed up with the wake turbulence generated by a large airplane. With a few exceptions each year, pilots of small GA airplanes successfully avoid accidents and incidents arising from wake encounters with large airplanes.
But we must remember that everything that flies creates wake turbulence. Crossing the flight path of that Canada goose is unlikely to cause a problem in even the smallest GA airplane. (Of course, colliding with that Canada goose is a different matter.) But can a slightly larger GA airplane present a threat of wake turbulence to a smaller GA airplane? Unfortunately, the answer is yes. A recent crash resulted from a Piper J3 encountering the wake turbulence of a Cessna 180.
And then, there are helicopters. Legacy wake turbulence training only gives a mention to the significant danger of a wake encounter with a helicopter. More recent training has addressed this danger more thoroughly, but this is easily missed by the pilot who participates only minimally in recurrent training.
What is different about helicopters? In short, helicopters do not fly the predictable paths expected from airplanes. We all know that helicopters will generally fly a traffic pattern opposite the direction of the fixed-wing traffic and frequently have different departure paths. But we also must be vigilant for the rotor wing folks while they are maneuvering around the airport. A helicopter will frequently hover taxi to reposition and the generated wake can present a problem for light airplanes taxiing. The wake can also drift across an active runway given the right wind conditions. A helicopter might make a normal approach to the approach end of a runway but then might hover taxi the whole length. That creates wake turbulence danger over the whole runway length, not just in the area before the helicopter touches down. Just like with fixed-wing aircraft, the intensity of the wake turbulence is dependent on the size of the helicopter but wakes may be of significantly greater strength than those from fixed-wing aircraft of similar weight. The strongest wake turbulence can occur when the helicopter is operating at lower speeds (20 to 50 knots).
Tower controllers will generally advise pilots of the location of helicopter operations. Pilots are on their own when operating at non-towered airports. At these airports, paying close attention to CTAF broadcasts is essential.
We must remember that wake turbulence is a real threat and deserves our attention. We must not let complacency cause us to believe that it will be okay “just this once.” We should also recognize that continuation bias gets stronger as we get closer to our destination. It can be a driving force to filter out threats including wake turbulence. A few minutes of extra time to stay clear of any wake turbulence is much better than weeks of recovery from a crash.
Reprinted from NASA "Callback" Issue 514 November 2022
A New Lease on Life
An experienced pilot’s guard and discipline were relaxed during a flight. Results could have been much worse.
■ I was flying home from work, low level over pasture, and failed to see power lines. I did not see the lines until I hit them. There was minor damage to the aircraft, damage to the power lines, and a fire was started from the downed lines. I have no injuries of any kind. I fly this route almost daily, and I think that because it was so familiar, I became complacent in my awareness of power lines when flying low. It was a beautiful, clear day, and I was distracted by the scenery. In the future, maintaining a higher altitude and being more alert of obstacles could eliminate the risk of this happening again.
Accidents discussed in this section are presented in the hope that pilots can learn from the misfortune of others and perhaps avoid an accident. It is easy to read an accident report and dismiss the cause as carelessness or as a dumb mistake. But let's remember that the accident pilot did not get up in the morning and say, "Gee, I think I'll go have an accident today." Nearly all pilots believe that they are safe. Honest introspection frequently reveals that on some occasion, we might have traveled down that same accident path.
Actual Accident Airplane. Photo Source: Arion Aircraft
This accident clearly illustrates the danger posed by the wake turbulence generated by a helicopter. Not only is the generated wake generally stronger than what would be generated by an airplane of similar size, but helicopters often fly unexpected flight paths.
This crash resulted in serious injuries to the 58-year-old private pilot and to the destruction of his Arion Lightning. It occurred in Pennsylvania in July 2022. The NTSB report includes the following: "The pilot of the light sport airplane reported that he was flying to an uncontrolled airport to attend an airshow later during the day. The destination airport traffic pattern was busy with several airplanes in the traffic pattern and a flight of three north of the airport. The pilot entered the traffic pattern by overflying the airport and crossing midfield onto a left downwind leg. At that point, a life flight helicopter reported 2.5 miles southwest. The pilot subsequently heard a report from the helicopter again and asked him where he was. The helicopter stated that he was on the right base leg for runway 11 and number two to land. The pilot of the airplane announced turning to final for runway 11. He was over the threshold at 20 ft above ground level when he saw the helicopter cross the runway several hundred feet ahead of him. The airplane then encountered the rotor wash, rolled right inverted and struck the runway, coming to rest on the runway."
Graphic Source: GoogleEarth (Annotations by GB)
Please note from the graphic above that the airplane never crossed the flight path of the helicopter. The wake extends outward from the generating helicopter and, like any wake turbulence will travel with the prevailing wind.
The NTSB accident report continues, "The pilot of the helicopter reported that he departed his home base about 2.5 miles from the airport to attend an airshow public relations event at the airport. He entered a right base leg for runway 11 and stated intentions to land No. 2 as there were four airplanes in the traffic pattern and airplane No. 3 (the accident airplane) was turning from left downwind to left base. The helicopter approached the runway numbers, sidestepped north to taxiway A1, and landed at a predesignated position on the taxiway for the airshow. After shutting down, the pilot was told by ground personnel that the airplane following him was involved in an accident."
Photo Source: NTSB
The NTSB Probable Cause states: "The airplane pilot’s inadvertent encounter with rotor wash/turbulence during short final approach, which resulted in a loss of control in flight."
Source: NTSB
The pilot's recommendation as shown above illustrates our point that helicopters do not always fly expected flight paths. It also shows the increased vigilance needed by all pilots at events with traffic congestion such as airshows and fly-ins.
Click here to download the accident report from the NTSB website.
Accidents discussed in this section are presented in the hope that pilots can learn from the misfortune of others and perhaps avoid an accident. It is easy to read an accident report and dismiss the cause as carelessness or as a dumb mistake. But let's remember that the accident pilot did not get up in the morning and say, "Gee, I think I'll go have an accident today." Nearly all pilots believe that they are safe. Honest introspection frequently reveals that on some occasion, we might have traveled down that same accident path.
Photo Source: RANS Owners Facebook Group
This crash happened in Ohio in September 2021. The 64-year-old private pilot, the builder of the RANS S20, died as a result of the crash. The NTSB accident report includes the following;"The pilot of the airplane was holding short of the runway for takeoff when he asked the pilot of an inbound helicopter to side-step to the taxiway so that the airplane could depart. The helicopter pilot reported that a side-step would have resulted in the helicopter flying directly over the airplane and that he side-stepped the helicopter toward the taxiway after clearing the airplane. An airport surveillance camera captured the airplane start the takeoff roll after the helicopter passed. Shortly after takeoff, the airplane entered a steep roll and impacted the runway. A postimpact fire ensued."
Photo Source: NTSB
Disturbingly, the NTSB report continues: "Toxicology testing of the pilot was positive for ethanol in blood, vitreous fluid, urine, gastric contents, and liver tissue. The ethanol in blood concentration (0.108 gm/dL) was associated with impairment, and alcohol consumption was fairly recent to the accident based on the concentration levels in the pilot’s body."
Graphics Source: Sequential stills from airport video (Collated by GB)
The NTSB report also states: "The pilot completed building the airplane about 5 months before the accident. The engine had a history of high oil and cylinder head temperatures, which may have been a factor in the pilot’s decision to depart so soon after the helicopter to reduce idling time on the ground."
"Based on the available information, it is likely that the airplane encountered wake turbulence from the landing helicopter during takeoff, which resulted in the pilot’s loss of control. It is likely that the pilot’s impairment from ethanol contributed to the accident."
Photo source: NTSB
The NTSB Probable Cause states: "The pilot completed building the airplane about 5 months before the accident. The engine had a history of high oil and cylinder head temperatures, which may have been a factor in the pilot’s decision to depart so soon after the helicopter to reduce idling time on the ground. Based on the available information, it is likely that the airplane encountered wake turbulence from the landing helicopter during takeoff, which resulted in the pilot’s loss of control. It is likely that the pilot’s impairment from ethanol contributed to the accident."
The analysis here is quite obvious. We must respect the strong wake turbulence generated by helicopters. This was a rather large helicopter, a Sikorsky S-76, but even smaller helicopters can generate significantly strong wake turbulence. We must recognize that there were likely external factors at work here causing the pilot to prioritize the engine temperatures over safe operation. Perhaps, as the NTSB states, his decision making was influenced by his impairment from alcohol.
Click here to download the accident report from the NTSB website.
Accidents discussed in this section are presented in the hope that pilots can learn from the misfortune of others and perhaps avoid an accident. It is easy to read an accident report and dismiss the cause as carelessness or as a dumb mistake. But let's remember that the accident pilot did not get up in the morning and say, "Gee, I think I'll go have an accident today." Nearly all pilots believe that they are safe. Honest introspection frequently reveals that on some occasion, we might have traveled down that same accident path.
This crash illustrates that everything that flies generates wake turbulence. The 25-year-old commercial pilot and the passenger were miraculously not injured in this crash but the airplane was substantially damaged. The event occurred in Nevada in October 2022 and involved a Piper J3F-60 entering the wake of a Cessna 180. The NTSB accident report includes the following: "The pilot reported that, while flying in formation inbound for landing, during the base leg to final approach turn, the airplane in front of his slowed down too much and he had to maneuver to give the airplane room to land. During the maneuver, the accident airplane encountered the preceding airplane’s wake turbulence and subsequently entered a spin at about 100 ft above ground level. The pilot was able to recover from the spin and collided with the ground hard in a wings level attitude. The wings and fuselage were substantially damaged. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation."
Photo Source: NTSB
The NTSB probable cause states, "The pilot's failure to maintain adequate separation during a formation flight, which resulted in an encounter with wake turbulence, an aerodynamic stall, and collision with terrain."
Pilot Narrative from NTSB Owner-Operator-Report
Pilot Recommendation from NTSB Owner-Operator-Report
Lessons learned here are as follows. First, we must always visualize where the wake turbulence might be when we are in the proximity of anything that flies. Second, formation flying adds additional risk which must be considered and managed. Third, airshows and fly-ins generally create significant traffic which also adds risk which must be considered and managed.
Click here to download the accident report from the NTSB website.
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