Failure To Follow Procedures

Failure to follow procedure continues to be a leading cause in incidents and accidents related to both flight operations and maintenance procedures. However, the aviation industry lacks insight into why such errors occur.

According to the Civil Aviation Authority, on average, a helicopter takes off and crashes with no one board once a year in New Zealand. The following reports exemplifying failure to follow procedures were retrieved from CAA Occurrence Briefs [1]

Accident Briefs

Occurrence #08/5260

Registration : ZK-HPR Aircraft Model : Robinson R44 Date and Time : 21 Dec 08 at 14:00 Location : Rangitata Island	Nature of Flight: AGRICULTURAL POB : 0 Injuries : nil Damage : Substantial
Synopsis: The pilot vacated the aircraft leaving the controls unattended in order to discuss the job with the landowner. The helicopter became airborne and rotated 180 degrees before landing on its skids, damaging the main rotor blades and tail boom. The aircraft flight manual contains a caution to never leave the helicopter flight controls unattended while the engine is running.	(Image embedded from Fillmore Gazette on 03 Sep 2009)

Occurrence #08/255

Registration: ZK-HKM Aircraft Model: Robinson R22 Beta Date and Time: 29 Jan 08 at 08:37 Location: Napier	Nature of Flight: PRIVATE OTHER POB : 0 Injuries : nil Damage : Destroyed
Synopsis: The helicopter was left unattended without friction or collective lock applied. The pilot heard the rpm increase but was too late to prevent liftoff and rollover. The machine was destroyed.

Occurrence #07/4122

Registration: ZK-HDB Aircraft Model: Robinson R22 Beta Date and Time: 17 Nov 07 at 13:00 Location: Haupiri	Nature of Flight: AGRICULTURAL POB : 0 Injuries : nil Damage : Destroyed
Synopsis: Collective lock not applied, and failure of factory friction nut, allowed collective lever to rise, and the machine flew unattended before crashing.	(Image embedded from NTnews on 03 Sep 2009)

Occurrence #04/4035

Registration: ZK-HHA Aircraft Model: Robinson R22 Beta Date and Time: 20 Dec 04 at 21:00 Location: Bonshaw Park Taupo	Nature of Flight: PRIVATE OTHER POB : 0 Injuries : Nil Damage : Substantial
Synopsis: The pilot vacated the helicopter, leaving the engine running. The collective moved up and the helicopter took off, turned 360 degrees, and went 10 feet into the air before settling in some pine trees.

Occurrence #00/93

Registration: ZK-HFF
Aircraft Model: Robinson R22 Beta
Date and Time: 18 Jan 00 at 07:00
Location: Big Bay

Nature of Flight: Hunting
POB : 0
Injuries : Nil
Damage : Substantial

Synopsis:
The helicopter was left idling while the pilot assisted his shooter to gut a number of deer. The pilot had applied carburettor heat, collective and cyclic frictions, and reduced rpm to a low idle. After about four minutes, the pilot heard the rpm increasing and when he looked round, saw the helicopter lift off and turn through 360 degrees. He attempted to catch it but was unable to do so before the main rotor struck a log and the machine came to rest on the heels of the skids and the tail section. The pilot then shut the engine down, noting that the collective friction had backed off to between half and three-quarters and that the lever had ridden fully up. He was of the opinion that the idling vibration level had been exacerbated by the nature of the surface (stony sand) on which the helicopter was parked, causing the friction to back off. He said later that he had a collective clip available, and in hindsight he should have applied it.

Investigation

There are several reasons for a pilot to leave a helicopter while it is running:

• Escort passengers to and from the machine safely (if there are no ground staff available)
• To accomplish quick task (load/unload stuffs/refuel)
• Speak to the person they are working for about the job (agricultural pilots to farmer)
• Other extenuating circumstances such as the risk of the weather changing quickly and not being able to start the helicopter again in such a hostile environment

Pilots leave their helicopters running primarily to save time. Many believe it can be done safely, and after doing it for years with no consequences it becomes a habit. Complacency pushes aside the very real possibility of the helicopter taking off without them.

How Does it Happen?

When a helicopter is on the ground a friction lock, and/or similar device, is applied to the collective to stop it being raised. If the friction lock is faulty,and the collective vibrates up, it will increase the pitch on the blades. The governor will then increase the power by a corresponding amount. If there is enough weight in the helicopter, this in itself would not be enough for it to become airborne, but sometimes the reduction in weight from the pilot getting out can mean there is just enough power applied to get the helicopter airborne.

A friction lock is also applied to the cyclic. If this fails the rotor disk will flop around. The yaw pedals also have the potential to creep or be bumped by a passenger. This can lead to the helicopter rotating on the ground and more than likely rolling over as a result. (Source: Vector) [2]

(Image embedded from Bush-Planes on 03 Sep 2009)

Lessons Learned

Pilots and operators should have strict safety procedures for leaving a helicopter unattended. These should cover the positioning of locks and frictions, RPM, limitations on wind direction and strength, instructions to be given to passengers who are left in the helicopter, the centre of gravity position and the effect on this when a pilot disembarks, and the distance a pilot is allowed to be away from the aircraft. The helicopter should be in continuous view of the pilot, there should be no extraneous people in the area who could walk into it, and dual controls should not to be fitted in front of a passenger. (Source: Vector) [2]

Remember – uncommanded fly-aways do happen, and you are taking a calculated risk every time you decide to leave a helicopter when it is running.

REFERENCES

1. CAA Occurrence Briefs Retrieved on 01 Sep 2009

2. Vector Retrieved on 2 Sep 2009

Want to know more?

item

explanation

---

Contributors to this page

Authors / Editors

AvMan