The police helicopter unit which serves Bristol is still under-staffed and needs outside help to deal with some emergencies, the Evening Post can reveal.

The team that operates the chopper for Avon and Somerset and Gloucestershire constabularies has been hit by shortages caused by a glut of transfer requests from air observers.

Last month, the Bristol Evening Post revealed at least three staff at Western Counties Air Operations Unit (WCAOU) asked to be moved to other departments after pilot Ian Kingston, who was originally sacked in December 2007 for dangerous driving, was allowed back to work.

When at full strength the unit, which provides air support and surveillance for the region, comprises an inspector, a sergeant and eight constables drawn from both constabularies. But it is currently only at half-strength with five fully trained observers – an inspector, a sergeant and three PCs – meaning the helicopter has been out of action for some shifts.

When asked last month whether the transfers had a detrimental effect on getting out to incidents and emergencies, an Avon and Somerset police spokesman said: “This is an operational issue that we’re not prepared to disclose.”

But now police have admitted the service has been hamstrung and other forces, such as Gwent Police, have been enlisted to help with call-outs.

Spokeswoman Catherine Foster said: “We cannot currently fill all shifts because there are a small number of vacancies currently at the Air Operations Unit. Procedures are already under way to fill those vacancies.

“Our fall-back position is to use mutual aid from other forces if there is immediate risk to life.

“This is exactly the same as what we do when our aircraft is unavailable to us because it is being serviced or if it has any maintenance issues.

“In turn, we are sometimes called upon to provide helicopter support to other forces when their own aircraft is not available.”

Denying the future of the Filton-based unit could be in doubt, Ms Foster said: “There is currently no intention to remove the Air Operations Unit from Filton. When the existing vacancies are filled and the new staff trained appropriately, the unit will resume its full operational service.”

Two officers begin training for the unit in September and a third will be operational in November. All air observers are experienced police officers. They have to pass a series of stringent tests before they are selected for training, then it takes seven weeks to train them up. After that, they have to pass an exam every six months to ensure they are performing at the highest levels.

Four ex-military pilots are directly employed by WCAOU to fly the helicopters.

One of those, Ian Kingston, was convicted in November 2007, banned and fined £2,000 for speeding down a 40mph coned-off area of the M5 near Cribbs Causeway at 110mph in his BMW.

He technically got his job back in April 2008, after appealing, but was not allowed back to work straight away. During his time off he was paid in full, but earlier this year Avon and Somerset and Gloucestershire police deemed he was fit to return to his job as a fully operational pilot.

Although the police confirmed air operative transfers have taken place, no reasons have been given as to why they made the requests.