Ibra wrote:
Curious question, was there any documented VFR mid-air collision in uncontrolled airspace above 4000ft agl worldwide? in VMC? in IMC?
Depends on your definition of “uncontrolled airspace”. There has been a mid air some 10 years ago north of Frankfurt (around TAU-VOR) in Airspace Echo.
But I agree to your general point: Midair-Collisions in Cruising flight are an extremely rare event – also due to the cruising level rules which most pilots actually respect.
In the US if you are on flight following ATC will most definitely tell you off if you stray too much from the hemispheric cruising levels which are mandatory anyway, see here.
Btw it’s always an altitude in the US, as the flight levels start at 18k ft and there’s no VFR in the Class A above that altitude.
Malibuflyer wrote:
And that means that whenever there is no specific reason not to use them (like weather, terrain, etc.) one just should use them
Well, I don’t agree here. The rule says you shall use the VFR levels and doesn’t consider any reason not to use them other than ATC clearance.
If the VFR levels available are 4500, FL85 and FL105. And FL85 is IMC, then you have to stick to either 4500 or FL105 according to the rule.
Terrain is considered by the mention of 3000 ft agl.
Malibuflyer wrote:
First chose the route, then look for the adequate cruising level (for direction of flight, terrain, airplane performance, etc.) and then check if there is a reason not to use this level.
Again, according to the rule, you must stick to these VFR levels and have very little freedom other than ATC Clearances which by definition only happen in CAS. But it seems like one MUST follow these OCAS and there are many situations where this becomes a huge nuissance.
On a final note: I agree with YOU, in that YOUR approach is the one that makes common sense and the one that I also use. But the occassions where this results in choosing a crusing level that violates the rule are numerous!
Malibuflyer wrote:
Depends on your definition of “uncontrolled airspace”. There has been a mid air some 10 years ago north of Frankfurt (around TAU-VOR) in Airspace Echo.But I agree to your general point: Midair-Collisions in Cruising flight are an extremely rare event – also due to the cruising level rules which most pilots actually respect.
I will check if a report is available, it could be intresting to know the extact circumstances: under weather? converging to some nav aid, airport or VRP? in cruise levels? or just “pure bad luck” in cruise…
Mid-Air collisions in cruise are very rare due to low traffic density and low section of aircraft vs size of airspace above 3000ft agl 
Hard to know if cruising randomly in altitude/headings filling whole airspace or flying in discreet blocks makes much difference but there is a threshold of traffic density where pure randomness no longer work and localized path is better, still means higher risk of converging traffic, this will be hard to see & avoid even with superior lookout
Most of the MACs I heard of in UK were in airport vecinity with majority being on ovehead join or on final to the runway
This recent one at Elstree (you may question “UK Ovehead Join” practice when you get a tire mark on your wing), luckily both pilots walked away…
https://www.mirror.co.uk/news/uk-news/two-pilots-cheat-death-after-10360257
Same for BGA gliding data load of MACs near airport vicinity, in circuits & sharing same thermal or turn point but not a single one in cruise even in similar task for the day…
skydriller wrote:
I have found that when I am cruising above 3000ft VFR “going somewhere” and I choose and relay to the FIS controller (Europe) that I am at FL45/55/65 etc, then half the time they reply confirming the FL and half the time they reply with a comparable altitude with Q
This never happened to me in: Spain, Portugal or Morocco.
I would very often fly above or on the Transition Level, the lowest usable flight level. And once above the Transition Altitude you must really use QNE rather than QNH regardless of whether you are IFR or VFR.
gallois wrote:
It wasn’t too long ago that the UK gave up the quadrantal rule in favour of the semi-circular rule used in most ICAO countries. Whether the air police will fine you is one thing, whether you have a mid air collision is down to you. I know which is more important to me.
I don’t think I have ever encountered other VFR traffic when flying above 3000 ft AGL. If there is someone up there, it’s mostly IFR, and in that case you’re in Class E or above receiving traffic information.
I’m not saying it doesn’t make sense to use this rule provided there are no other reasons not to use it. But the law seems more restrictive: you MUST use them.
NicR wrote:
These are not mandatory in the UK; indeed randomisation of cruising levels is encouraged.
One of few UK deviations I actually agree with since they make more sense than SERA/ICAO.
Alpha_Floor wrote:
since they make more sense than SERA/ICAO
Hard to say without any real data or simulations but it surely depends on traffic density, airspace size and speed deltas
Ive never flown in Spain, Portugal or Morocco… 
Thinking about it a bit more, this was variously in France (definitely) and in Germany, possibly crossing the FIR boundary over the Baltic at FL65 and into German Class E? ISTR that crossing over the Channel at FL55 and into the Solent CTA Ive been cleared at FL55 at least once rather than at an altitude on QNH.
Regards, SD..
Alpha_Floor wrote:
The rule says you shall use the VFR levels
The word “shall” in legal context means that you have to unless there is a reason not to. Weather, Terrain, etc. would be such a reason – but yes, you had to consider another valid FL before “flying random”
Ibra wrote:
I will check if a report is available, it could be intresting to know the extact circumstances: under weather? converging to some nav aid, airport or VRP? in cruise levels? or just “pure bad luck” in cruise…
A little bit all of the above: Converging at a traffic aid, one of the two in descend and therefore not observing VFR flight levels, low sun reducing visibility, …
