Right, so we're picking up a very specific operational situation — Page 481, Lesson 644

Right, so we're picking up a very specific operational situation. We've just been talking about what happens when you're cruising along and you lose the ability to make radiotelephony contact with ATS — that's Air Traffic Services. Now, the rule says that if you find yourself in that position, the pilot-in-command should, wherever possible, do two things. First, you should attempt to broadcast warnings on the VHF emergency frequency — that's 121.5 MHz — and on other appropriate frequencies, unless considerations aboard the aircraft dictate otherwise. So if there's a reason on board that makes broadcasting unsafe or unwise, you're excused. But beyond just the radio, you should also use other equipment when it's advantageous and circumstances permit — things like your on-board transponder and data links. The point is, you're trying to get your situation out to anyone who can hear, by any means available. Second, you should proceed in accordance with any applicable special procedures for in-flight contingencies, where such procedures have been established and promulgated. That means if the region you're in has published a specific procedure for this exact emergency, you follow it. Now here's the key part — what if no regional procedures have been established? Then you have a specific rule to follow. You proceed at a level which differs from the cruising levels normally used for IFR flight in the area. And the amount of difference depends on your altitude. If you're above FL290 — that's Flight Level 290, or 29,000 feet — you offset by 300 metres, which is 1,000 feet. If you're below FL290, you offset by 150 metres, which is 500 feet. So you're deliberately choosing a level that's not the standard one, to reduce the risk of collision with traffic that's following the normal rules. Now, let's move on to a different part of the regulations — extracts from Annex 6, which deals with the Operation of Aircraft, specifically Part I, International Commercial Air Transport. This is about how commercial operators must equip and prepare their aeroplanes. First, security of the flight crew compartment. On any aeroplane that has a flight crew compartment door, that door must be capable of being locked. And here's the critical detail — it shall be lockable from within the compartment only. So the crew inside can lock it, but no one from outside can. That's a deliberate design choice for security. Second, the aeroplane search procedure checklist. An operator must ensure there is on board a checklist of the procedures to be followed in searching for a bomb in case of suspected sabotage. So if you suspect someone's planted a bomb, you have a defined search procedure. But it doesn't stop there — that checklist must be supported by two more things. Guidance on the course of action to be taken should a bomb or suspicious object actually be found, and information on the least-risk bomb location specific to that aeroplane. That's the spot on that particular aircraft type where a bomb would cause the least damage if it detonated — and the crew needs to know exactly where that is. So to tie it together — we've got two distinct areas here. One is the contingency procedure for lost communications in cruise, with that specific altitude offset rule. The other is the security requirements for commercial aircraft — the lockable cockpit door and the bomb search checklist. Both are about managing risk in abnormal situations, but they're very different kinds of risk.