Propeller Safety Promotion
This safety notice forms part of the Australian Pilot Training Alliance safety promotion for July 2017 and addresses Identified Hazards of aircraft propellers.
The article will identify hazards of the aircraft propeller, cite logged and known incidents, and promote safety behaviours to control the risk of propeller hazards.
- A simple fault in the ignition system, a single broken wire, may render the propeller “live”. A “live propeller”, if moved, even slightly, may cause the engine to start.
- An incorrect shut-down procedure may leave the engine “primed” and ready to fire, should there be a fault in the ignition system or the ignition is inadvertently left on.
- An aircraft starting without the pilot giving adequate warning to unobserved personnel.
- Incorrect starting procedures leading to a rapid increase in RPM, causing the aircraft to move forward unexpectedly.
- A spinning propeller may not be visible to the human eye, especially in low light levels.
- An operating engine and propeller may not be audible in conditions of high ambient noise levels.
- An aircraft taxiing into unobserved personnel especially in low light levels.
Incidents logged by Melbourne Flight Training’s Safety Management System
- On two occasions “hot” starter motor switches have resulted in the propeller being turned by the starter motor when the master switch was selected on with the key-switch in the off position.
- A magneto defect has resulted in the propeller being “live” (the magneto operational) in the apron parking area.
- The ignition switch was left on overnight when the crew did not complete post flight checks.
Other incidents which Safety@APTA had a direct connection.
- Safety@APTA’s had an experience where an engine started and ran momentarily when the propeller was manipulated. On this occasion, the key-switch was in the off position and the engine controls were in the safe position. A defective key-switch resulted in a magneto remaining “live” in the off position.
- A pilot known to Safety@APTA was injured when an engine started when the pilot rested his elbow on the propeller while waiting for an aircraft engineer to assist in starting the engine. The propeller moved fractionally under the weight of the pilot’s arm, the “impulse coupling” engaged, a cylinder fired and the pilot was struck in the head by the propeller.
- An engineer, know to Safety@APTA reported, that an engine started and continued to run in a hangar. The propeller was being manipulated in preparation for a cylinder compression check.
- Instructors have been observed by Safety@APTA exiting Piper Warriors by stepping forward from the wing with the engine operating.
- Pilots and maintenance personnel have been killed by walking into propellers knowing that the engine was operating.
- A sickening number of people have been killed and injured “hand swinging” propellers.
Australian Pilot Training Alliance Operations Man
OM2 1.1.13 extract…engines shall not be started until the Pilot is satisfied that the operation of
the engine or any controls will not pose a safety risk to any person outside the aircraft.
OM2 2.5.8 extract…Anti-collision beacons where fitted and navigation lights are to be turned on
immediately prior to engine start and to remain on until the engine is stopped…
“Hand swinging” of propellers is not permitted where alternative means of starting the aircraft engine are available. “Hand swinging” for aircraft not fitted with “impulse coupling” is not permitted. In the exceptional case where no alternative exists, this may only be attempted by appropriately trained personnel and with approval from the Head of Operations. OM2 1.1.13 and OM4A 2.2.2.
Propeller Safety Precautions
Show that it’s safe
Make keys visible to other crew members indicating that the ignition key-switch is in the safe position. If the keys are not visible, this will alert crew members that the ignition switch may be on, and to remain clear of the propeller. Before start-up ensure that the keys are out of the ignition switch and placed visibly on the glare-shield.
Make sure it’s safe
The first item in a Daily or Pre-Flight Inspection is to ensure that the engine controls are in the safe position. Ignition switch off, keys out and placed visibly on the glare-shield. Mixture Idle Cut Off. Throttle closed. Master switch off. Park brake on.
Keep it Safe Airside-Maintain awareness
When airside be alert for aircraft starting-up and taxiing, maintain a lookout for you and your passengers. Do not approach aircraft with crew in the control seats. Do not approach aircraft with lights displayed. Walk behind aircraft fitted with forward mounted propellers. Listen out for start-up warnings. Airside is not the place to use PEDs, Portable Electronic Devices.
Do not approach aircraft that are not displaying lights unless acknowledged by a crew member that it is safe to approach. Wear Hi-Vis vests at night.
Safety procedure before selecting the battery master switch on:
- Take care to observe that the propeller area is clear
- Clearly announce: “STAND CLEAR, BATTERY MASTER COMING ON”
- Wait for a response from anyone that is nearby and to give them time to get clear
- Then, and only then, turn the battery master switch on
Safety procedure before engaging the starter
- Confirm that the aeroplane is in a safe position to start (clear of the parking area, other aircraft and buildings etc.)
- Confirm that the aeroplane beacon and navigation lights are on
- Take care to observe that the propeller area is clear and that no one is approaching the aeroplane
- Clearly announce: “STAND CLEAR, ENGINE STARTING”
- Wait for a response from anyone nearby and to give them time to get clear
- Then, and only then, engage the starter
Brief passengers on propeller safety
Brief passengers not to approach propellers and to remain behind parking lines in MFT’s “PARKING AREA” for their safety. Brief passengers to remain in the “safer area” while waiting to board aircraft.
Magneto safety check at shut-down
The magneto safety check before shut-down is an important guard against unknown “live propellers”. At idle power, typically at or below 1000 RPM, the ignition switches are selected from BOTH to LEFT and then to RIGHT, before selecting BOTH again. Normal operation of the magnetos will be indicated by a slight RPM drop when the LEFT and RIGHT magneto are individually selected. If no RPM drop is observed when the LEFT and RIGHT magneto are individually selected, a defect has occurred that will render at least one magneto live after shut-down.
CAUTION. Inadvertently selecting the ignition switch to the OFF position before reselecting the switch back on at higher RPM may result in unburnt fuel in the exhaust system igniting and causing damage to the aircraft exhaust.
Safely stop the engine
Stop the engine by moving the Mixture control to the Idle Cut Off position (Mixture ICO). The momentum of the engine and propeller will continue to rotate the engine, pumping remaining fuel vapour from the cylinders and induction system before it stops. This will purge fuel from the cylinders at shut-down decreasing the risk of the engine starting should the ignition be inadvertently left on or a grounding fault exists and the propeller is manipulated.
CAUTION. Should an aircraft engine stop as a result of inadvertently selecting the ignition switch off, re-start and then shut-down normally using Mixture ICO.
Safety behaviour as a habit
Always behave around propellers as if they are “live” and spinning. Imagine a no-go zone surrounding the propeller from wing tip to wing tip in an arc of the radius of the same dimension in front of the propeller. Habit forming of this kind may be the only guard against distraction that allows someone to walk into a known spinning propeller!
Never walk in front of a starting aircraft, an error in start-up procedure may have the aircraft unexpectedly move forward.
Never walk in front of a taxiing aircraft, the pilot controlling the aircraft may not see you, especially for some types and in conditions of low light.
Do not commence a Daily or Pre-Flight Inspection until the engine controls are confirmed to be in the safe position and treat the propeller as if were “live”.
Move the Propeller Safely, if it must be moved
Propellers may have to be moved at times, to attach a towbar or to position the propeller for inspection. Before moving the propeller, ensure the engine controls are in the safe position and the aircraft is restrained from being able to move: parking brake on, wheel chocks positioned or tied down. Move the propeller in such a way, that should it start, nobody could be injured. Stand behind the propeller. Prevent yourself from falling forward into the propeller by bracing yourself:
- By firmly grasping the hand hold on the Cessna 152/172/182
- By firmly grasping the engine frame through the open cowling hatch on the Piper Warrior
- By firmly grasping the open oil filler hatch on the Piper Archer/Seminole
If any doubt about the safety of the propeller exists, do not move the propeller.
Aircraft engine accessories may suffer damage if the propeller is moved backward (anti-clockwise from the pilot’s perspective for aircraft operated by APTA); however, the ignition system cannot operate if the propeller is moved backwards.
Report Ignition System Defects or Abnormal Magneto Safety Check Results
Should individually selecting the Left and Right magneto result in no decrease in RPM there is a fault in the ignition system that must be reported. Do not manipulate the propeller and report the defect to MFT as soon as possible. The Maintenance Release must be endorsed and precautions to alert personnel to the hazard of a “live” propeller put in place.
Propeller Safety is up to you
Risks associated with propellers can almost be completely eliminated by ensuring that propeller safety behaviours and precautions are strictly practiced.