Take off/Land "at your discretion"?
 

As far as I understand it, an aerodrome controller would issue a take off/landing clearance with the caveat "at your discretion" if the operating surface and/or the aircraft in question is not visible (or only partially visible in the case of, say, a runway). So far so good, but where is that set down in writing? I've trawled through several docs without success. On top of that, isn't every take off/ landing clearance ultimately at the pilot's discretion no matter the conditions?

This phraseology would be used by a flight information service officer (FISO) rather than a controller. The difference is it's advisory since a FISO is not entitled to issue a clearance. Practically speaking, it means the same but legally, if you subsequently collide with someone it's your fault not his.

ShotOne, thanks for that.
I have witnessed this phraseology being used by aerodrome controllers in many locations - normally in situations such as low vis ops or helis operating from "uncontrolled" surfaces. Perhaps it's crept in from FISO speak or maybe as a reminder to the pilots that "I'm not visual with you and/or some or all of your intended operating surface" or "I can't guarantee that surface is 100% safe for use".
I would like to see the document/publication that approves the use of that phrase in a controlled environment. I have not found it in CAP413.

Why is this on Military Aviation??

CAP 413 page 48 para 4.110

I can remember being in the back of a Fuga being given clearance to do a beat up at our discretion, surprised wasn't the word when we found a Cessna 172 at the other end climbing out, at least he wasn't coming towards us!

4.110 At aerodromes with air traffic control service, when helicopters land or take-off at locations not on the manoeuvring area (e.g. apron, maintenance area, sites adjacent the aerodrome), or locations not in sight of the VCR, or unlit locations at night, the appropriate phrase ‘LAND AT YOUR DISCRETION’ or ‘TAKE-OFF AT YOUR DISCRETION’ shall be used to authorise the manoeuvres. Relevant traffic information on other aircraft (airborne or on the ground) shall also be passed and the name of the designated landing/departure point/area should be stated.

Perfectly acceptable in a controlled environment.

Bill, simply because I was asked the question at a military airfield.
Thanks to everyone else, I'll look closer next time.

only heard it once - 2 MR2s landing at Marshall Island (International) Airporthttp://rmipa.com/airports/ . You also had the option of turning on the airfield lights using R/T. A few locals wandered over to have a look at the mighty MPA but seeing as 747s apparently regularly landed there, they weren't that impressed.
And there is your link to mil aviation :)

Tenuous?!!

Bill
 

Why is this on Military Aviation?

Sometimes military aircraft land at civil airfields, including LHR.

I had an ex-Herc mate who, when he was on BA 757s, kept going on at me over a beer - "Why do you LHR controllers give us 2 minutes behind a Heavy when we rotate way before the place that they had?".

My reply was that the rules don't allow me to shorten the time behind a Heavy, but if you or anyone else ask me for clearance for take off stating that you don't need the 2 minutes then my reply will be " Cleared for take off at your discretion ", strictly speaking I should also have reminded him he needed 2 minutes behind a Heavy, but as they had already told me that didn't want 2 minutes I omitted that!

Thankfully I reached retirement without an incident that would have caused a " No coffee " interview!

This option also applies at military airfields. I have witnessed it at a military airfield in exactly those circumstances - a rotary landing directly on to a dispersal. It took me by surprise at the time and I had to look it up.

Oh, the perils of posting a thread in the WRONG forum. How very dare I.
The subject was raised by a military pilot (fixed wing) operating at a military airfield and the controller involved was also military. I now have the answer, thank you to the relevant posters above for their input.
Excuse me whilst I march myself off to the guardroom for some re-education in forum etiquette.

The most important word in our military instructions from ATC to an aircraft was "clear".
The implications of using it, were that excluding unknown actions, the request by a pilot to do something was safe to allow.
At various units I controlled at with mixed fast jet and helicopters, there were occasions that we couldn`t see where some helos were ground taxying from. So, after the pilot requested taxy clearance, we replied omitting the word "clear" because we couldn`t guarantee his/her movement in an area we had no control over.
This always seemed to me to be a huge CYA and we asked the crews if they were aware of our missing word and the reason. They all replied that they didn`t really appreciate what we had implemented and perhaps consultation first would be preferable!
Sounds like a plan in any aviation structure to my thinking.

I asked the ATC at Hawarden that when they forever refused our Police helicopter to depart due to wake turbulence. Their excuse was that they were legally obliged to make us wait the required amount of time. They refused to budge despite the fact that I could draw representative flight paths to show that we never got any where near the wake.

Never had the problem at Liverpool. A simple "request immediate departure" and we were cleared to go.

What about if a helicopter arrived unexpected at a Naval Air Station, out of scheduled hours, and called up on local VHF asking permission to land, and was then heard by say Fire Station or security on their own radios> Would it be okay for them to say land at your discretion". Clue - I have actually heard this and witnessed it. Is that acceptable?

I should imagine it's because parallel runway Ops is 760m for wake turbulence. If the Fuga has just landed / got airborne you're stuck for 3 mins unless a local Risk Assessment can be argued to allow you to depart. But with 2 upside down heli's recently (Cambridge and Gloucester) where adjacent aircraft were in excess of the guidance yet still created a safety event it's a brave person to sign that one off.

To be accepted in the Mil Forum, one must confine one's remarks to outdoor grilling devices only.

CG

Edit: Confine your remarks to a specific brand of outdoor grilling device, else you will be called out of order.

I never liked allowing pilots to do things at their discretion. It implied a complete carte blanche to the wild children of aviation ;)

I did, however, once clear a Single Pioneer to land across runway 36 at Tengah "at his discretion" due to a strong crosswind. Nothing else was moving, he approached across a quiet Dispersal, touched down on one side of the rw and just taxied quietly to his dispersal on the other side of the rw.

I was a very naughty ATCO, but at least I kept the traffic moving ;)