7-day visa-free entry to UK for foreign aircrew - does it work in GA?

[Ultranomad]

According to the rules posted on UK Border Agency's website, aircrews from visa countries get a visa-free entry clearance:

CRM2.3 Aircrew arriving as a crew member of an aircraft

Under Section 8(1) of the Immigration Act 1971 a person who arrives as a crew member of an aircraft does not need leave if he is under engagement to leave within 7 days on that or another aircraft (or until the aircraft departs) unless:

• there is a deportation order in force against him;
• he has at any time been refused leave to enter and has not since been given leave to enter or remain; or
• an Immigration Officer requires him to submit to examination under Paragraph 13(1) to Schedule 2 of the 1971 Act.

CRM2.4 When do aircrew need entry clearance?

Airline crew members do not need prior entry clearance if they:

• are operating crew (including stewards and stewardesses*);
• are holding their licences or valid crew members' certificates or passports; and
• are departing, as a member of the crew, on the same aircraft from the airport at which they arrived or within seven days on another aircraft (crew intending to stay longer than seven days must have entry clearance. Those who wish to extend their stay after entry must apply in the UK for leave to remain).

An extensive search on Internet has not revealed any indications how this 'engagement to leave' should be demonstrated in case of GA, nor any mention that this manner of entry does not apply to GA. Does anyone know, has anyone tried? For example, would a GAR form with both arrival and departure dates filled in count as such an engagement?