Separation with preceding aircraft during emergency
 

My question is for tower controllers.

You have only one runway, used for landings and departures. There is an aircraft making a straight in approach for landing. It is about 30 Dme to touchdown. Under APP controller.
APP controller is calling you and relays that, approaching traffic declaring emergency (engine problem).

At this moment you have two aircraft under your control. One is just reported outer marker and you already instructed to cleared to land. The second is about 12 DME. You instructed to report outer marker.

Do you give instructions to these two aircraft to go around in case, they may block the runway before your real emergency? Or you keep your optimism and let them land?

There are no clear rules to govern this situation, It is the local controllers call. 30 Dme 7-9 minutes out for the emergency aircraft, traffic over outer marker I would probably let it land. 12 Dme it would depend on winds, who is the aircraft etc. plus depending on airport, do emergency vehicles need to cross taxiways the second aircraft will use. I would probably send the second around but let the first land. But unless your there making the call it is all very subjective. At least in FAA land.

There may be local ATC procedures to cover this.
These will differ from unit to unit and will be based on a variety of factors.

One would hope this this would be covered in local ATC instructions.

In the UK it is called 'runway sterilization/sterilisation'. Our state equivalent of ICAO Doc 4444 PANS/ATM, the UK MATS Part 1, says;

...and our local ATC manual (MATS Part 2) states the circumstances under which we must sterilise the runway ahead of landing emergency traffic and the distance from touchdown (of the emergency traffic) at which this must take place.

It also depends upon the nature of the emergency. A 4-engine a/c with one shut down as a precaution is one type of emergency. A 2-engine a/c with, say, an uncontained compressor failure which might then have caused airframe damage and / or fire is also an emergency. Very different types though.

My considerations would be: is the emergency able to go-around and divert in case the runway gets blocked ahead of it? If not, I'd sterilise the runway as soon as possible.

E.g. P3 Orion emergency one engine out, require 4 hours holding to burn fuel (no dump available...) :bored:

We were recently told to go around for emergency traffic behind when we were at about 3 miles from touchdown on 16R at FCO. Vectored round for another approach, I was a bit miffed to hear the emergency traffic given his landing clearance almost ten minutes after we'd gone around. If we'd been allowed to land we'd have had half the passengers off by the time he landed. Ho hum.

An extra mile in front used to work fine but the whole system is riddled with paperwork nowadays.

Thanks for replys. So you are lucky if this situation is mentioned in your local emergency manuals. But unlucy we are not.

And as i understand, the decicision changes person to person, unit to unit.