Hi Bob and Richard,

I am surprised by a few of the LOSA statistics.

1) One which stands out is the the observation that 5% of airline flights feature an unstable approach BUT only 5% of those result in a missed approach.

Under what conditions is an approach defined as unstable? It must be a rather all-encapsulating definition if so many of those pilots audited 'just put her down anyway'.

2) Secondly, the audit reveals that 30% of Undesired Aircraft States (UAS) can be linked back either directly, or via an error to an initial threat. I find this to be less than expected.

What kind of events cause the other 70% of UASs, if not threats or human errors?

Cheers, rubber

Hi rubber,

An unstable approach does not automatically mean an unsafe approach. It infers the approach was not flown within defined tolerances and as such the margins of safety were compromised to a greater or lesser extent. In only 5% of these cases, the the approach was so bad, the captain threw it away.

According to the TEM paper " Defensive Flying for Pilots: An Introduction to Threat and Error Management " put out by the Uni Texas, those statistics actually read as: "About 30% of all UASs occur as part of a chain of events that starts with a threat
that is not managed well and leads to a crew error, which in turn is mismanaged to a UAS." i.e. 30% started as a threat, progressed to an error which ended up as an UAS.

It is possible for a threat to result in an UAS without any crew error involved e.g. sudden windshear on approach leading to a drop in approach speed: this is an external threat leading to a UAS but no crew error was involved.

A UAS may also result also from a previously unmanaged UAS e.g. pitot heat not turned on in icing conditions (UAS), the aircraft loses ASI functionality during the approach.

Cheers,

Rich