Safety Alert 00-01 - 26 April 2000

Subject: Damage to CAP Aircraft -- Prop Strikes

An alarming trend has surfaced during the first quarter of CY 2000. We are experiencing prop strikes at an alarming rate. In 1999, we had 3 prop strikes for the entire year. Compare that to 6 prop strikes we've had during just the first quarter of 2000. This represents an 800% increase! Prop strikes however, are not the problem. They are simply the result of pilot deficiencies and sometimes, complacent attitudes. These problems are occurring, as you might expect, in the taxi and landing phases of our flight operations. Let's explore these incidents in an attempt to understand why they're happening and how to prevent them in the future. Use them also to trigger discussion of similar hazards that may pose a threat to your flying operations.

1999 Prop Strikes:

- The first prop strike occurred during a hard, night landing that was so severe that the nose gear collapsed and the windshield cracked. The pilot landed in gusty crosswinds, possibly in excess of the aircraft's demonstrated crosswind capability. The investigation also revealed that his approach was high and fast.

This mishap chain had several links - any of which, if eliminated, might have prevented this one. It occurred at night when there are less visual cues. The crosswind component was near the max with the gust factor possibly exceeding the limitation. Last, but not least, the approach was not stabilized. How could this one be prevented? Perhaps, early in the approach when the winds were confirmed near the limit, another airfield with a more favorable runway orientation could have been chosen. Another option that could have been exercised further down the approach is a go-around; always a good decision when you're off the normal glide path and not at the manufacturer's recommended approach speed.

- The next one also involved a bounce during a night landing. Unknown to the pilot, the prop tips were damaged during that landing. The pilot made two more uneventful takeoffs and landings. While securing the aircraft after the flight, the pilot noticed the damaged prop tips. Because the aircraft was not available for this sortie until after 11PM and the pilot had been up since 5AM, fatigue was probably a factor. Prior to this event, the pilot had only five night landings in the C-182.

Here again, variables may have been stacked against the pilot - night, fatigue and a relative newcomer to night landings in the C-182. Any of these items by themselves would usually be overcome by the pilot, but when combined, presented a formidable challenge. Remember, if you have the slightest suspicion that a prop strike may have occurred, it's always prudent to park the aircraft and examine it before continuing the flight. The slightest damage can set the prop up for failure.

- The last prop strike of 1999 involved a pilot taxiing on grass. After taxiing over a slight crest, the nosewheel dropped into a depression concealed by grass. The bouncing motion allowed the prop strike to occur. The pilot later found that two other aircraft had struck their props earlier in the same hole! The FBO manager was finally persuaded to barricade the hazard until the hole could be filled in.

CAP operations occasionally demand that we taxi off of paved surfaces. When we do however, it's important to realize that many of the obstruction clearance safeguards disappear as we leave the hard surface. Hazards can be hidden by grass and terrain irregularities can cause the aircraft to bounce during taxi. Taxi speed should be significantly decreased and the control yoke held back to maximize nose strut extension and the clearance between the prop and any hidden hazards on the ground.

First quarter 2000 prop strikes:

- While taxiing an aircraft from its parking spot to a maintenance hangar after sunset, the pilot inadvertently taxied off of the taxiway into soft mud. The nosewheel sank in a depression, which allowed the propeller to contact the ground. The engine continued to run, so the pilot continued to taxi back to the paved surface and ultimately to the maintenance hangar. After the engine was shut down, the prop was found damaged during the post-flight inspection.

This mishap not only involved loss of control that resulted in departure from the taxiway, but also a lack of judgement in continuing to taxi after entering soft mud. If you ever find yourself in this situation, remember that adding power usually drives the nosewheel deeper in the mud, thus increasing the chance of a prop strike. Tugging the aircraft out of the mud is a better choice.

- During a CAPF 5 checkride, a short field landing was unsuccessfully attempted. The aircraft touched down in snow approximately 20-30 feet short of the runway threshold. The nosewheel yoke broke off leaving only the nose strut to support the front of the aircraft. Without the nosewheel, the prop struck the ground and the runway as it skidded to a stop on the right side of the runway.

The main point here is how some precautions can ensure a margin of safety while practicing short field landings. By practicing this maneuver at a long, wide runway and visualizing a short field overlaying this runway, you can constrain yourself within the "short" runway and still have paved surface at both ends if things don't work as planned. Airspeed control is especially critical during this maneuver. If the approach is not stabilized, remember that a go-around is always an option.

- During a freezing, early morning, the mishap pilot attempted to start the aircraft engine. The starter was unable to turn the prop with enough authority to start the engine. The pilot got out of the aircraft and positioned the prop where it would travel the farthest before encountering compression. This was a technique that had worked in the past and it worked this day on the third try. Because the pilot had to exit and enter the aircraft repeatedly, the pilot started the engine with his seat in the full aft position. The parking brake, however, was set. After the engine started, the pilot was distracted by an intercom problem in the rear seat. As he was facing rearward, a passenger noticed the aircraft moving in a left turn and yelled to the pilot. Because the pilot's seat was in the aft position, he could not reach the toe brakes before the prop struck a metal pipe railing.

Whenever nonstandard events or actions enter a flight operation, extreme care should be taken until normal ops are resumed. Nonstandard operations often set the stage for mishaps. The nonstandard engine start described here, set up more nonstandard activity such as starting the engine before all of the items on the Before Starting Engine checklist had been accomplished. If the checklist had been accomplished, the seat, seat belt and shoulder harness would have been adjusted and locked and the mishap would not have happened.

- A cadet, student pilot was flying solo when he experienced a couple of hard landings. It is suspected that a prop strike occurred during one of those hard landings. The cadet, however, did not experience any changes in the flight characteristics after the hard landings. The next scheduled pilot found the prop tips damaged during the preflight inspection.

Knowledge and skill could have helped this cadet. The knowledge that hard landings can result in prop strikes and that in the excitement of a hard landing, the prop strike may not be noticed. We discussed the danger of continuing flight with a damaged prop earlier in this safety alert. It's important that all our pilots, including our cadet aviators, understand the importance of inspecting the prop after a hard landing. A skill that can help to prevent hard landings is adding the right amount of power during an early or over flare. This technique can be learned by practicing with a CFI. Go-arounds should be practiced more. We all become programmed to land, but frequent go-around practice can make this maneuver second nature when needed.

- While taxiing out to fly an AFROTC Cadet Orientation flight, the pilot taxied across a parking row instead of following the taxiway. He accelerated while crossing over a tiedown rope and it was picked up by the prop. Before the engine could be stopped, the tiedown rope had damaged the prop, spinner, bulkhead and the lower cowl.

Normally, a pilot can taxi into a parking spot over a tiedown rope without the prop picking it up. This is because the aircraft is close to idle power and slowing down. To increase power and accelerate through a tiedown area is just asking for trouble. There are numerous hazards in a parking area - chocks, grounding wires, ropes, tiedown cables, people and other aircraft. It may take a little longer to taxi on the taxiway, but you can feel confident that you'll encounter fewer hazards.

- After refueling, the pilot taxied on a paved taxiway to a grass tie-down area. When the aircraft entered the grass area, the nosewheel entered a storm drain, which allowed the prop to strike the ground.

The hazards of taxiing off of a designated taxiway have already been covered. The risks are even higher when taxiing on unpaved surfaces. Hazards can be hidden, so extreme caution is warranted. Holes, mud, rocks, drains and a wide assortment of other obstructions can lie in wait, concealed by grass.

The Bottom Line

Of the nine mishaps described, four occurred during landing and five happened during taxi. During the landing phase of flight, loss of aircraft control, for a wide variety of reasons, was the leading cause. Factors such as wind, fatigue, bad judgement and lack of proficiency certainly contributed to the loss of control. A renewed emphasis is needed on landing proficiency that highlights a stabilized approach and the value of a well-practiced go-around. Crosswind and wind shear training, under the watchful eye of a CFI, would certainly help prepare pilots for these challenges.

During the taxi phase, hazards were associated with straying from taxiways, as well as operating on unprepared taxi surfaces. Nonstandard operations and bad judgement were contributing factors. An emphasis should be placed on appropriate taxi speeds and the increased risks that occur off the taxiway.

Thanks for helping to turn this trend around. Fly (and taxi) safe. -- GKW --

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