when have you used 1000ft on top?

[CharlieMaso]

I teach a course in aviation and im trying to collect real world examples of operational situations where pilots might request to use 1000ft on top. Im in BC with lots of high terrain and so far have two examples:

1. a pilot is on an airway with an MEA above 10,000 or on a direct track with an AMA above 10,000. Using 1000ft on top on a clear sunny day would allow them to cruise below 10,000 for extended periods without meeting the oxygen use requirements of CARS.

2. An aircraft is descending into an airport with surrounding high terrain. Controllers are unable to assign lower altitudes due to high MVA's. There is a low cloud layer, but peaks are visible through the clouds. Descent could be more orderly using 1000ft on top rather than staying high till a navaid and shuttling down or doing steep descent step downs as the controller clears you lower.

Any other situations you have used 1000ft on top to your advantage? Thank you.

[oldtimer]

Departed YQL in bright sunshine, VFR to YPE. Wanted to stay low due to winds. YYC and YQF are down in low cloud but YPE was scattered cloud. 1000 on top allowed a low altitude VFR trip the whole way. Not enough comfortable fuel for an IFR alternate due to winds. Also stayed on top to stay out of ice.

[CharlieMaso]

Im a little confused. It sounds like you are talking "VFR over the TOP" as opposed to "1,000ft on top".

If you are indeed talking 1,000ft on top you would still have to carry IFR fuel reserves as you are still on an IFR flight plan when operating 1,000ft on top.

Thanks for getting my thread started!

[Big Pistons Forever]

I have never used 1000 on top on any flight, and frankly can't see a scenario where I would use it. It's only value is as another toughie trivia question for exams for the real world, practical operations, free zone like you often find at an FTU......

[fish4life]

i'm confused now... what is it?

[Stinky]

I think it's one of those things that are never used. I'm sure if you requested it you'd get a confused response from a controller and he would just ask if you needed a block and would assign you that. I've never heard it requested, don't spend time on it in a groundschool. Mention it and move on. Requesting a block or a descent at pilot's discretion will accomplish what you need.

As for your first example, if I read it right. You won't be able to remain IFR if you're below the controllers minimum altitude so I'm not sure that would be a valid example. That situation would be where you use a flight plan that transitions from IFR to VFR or vice versa.

It's like learning how to fly offset an airway. I've requested it to avoid a line of weather and get the confused response with "can you just tell me the heading you want now and I'l get you back direct later?"

[Hedley]

Never used it in 20 yrs of IFR flying.

Weirdest thing I probably ever did (wrt civilian IFR) was formation IFR. ATC thought that was pretty strange.

[co-joe]

Yeah stinky it's one of those obscurities like the composite flight plan or even a contact approach for that matter. I think the first time I did one of those was because someone ahead of us asked for one and got it and we were like "hey I wanna try that too..."

Try declaring "minimum fuel" one time just to hear confusion in ATC voices... 1000' on top I think lets you fly a non IFR altitude to stay clear of IMC but never used it or even heard it used. A block altitude is much more useful if you're say letting one of the medics/ AME's/ girl you found on the reserve fly for a while and they can't really hold altitude all that well or something.

[Joe Blow Schmo]

It's like learning how to fly offset an airway. I've requested it to avoid a line of weather and get the confused response with "can you just tell me the heading you want now and I'l get you back direct later?"

Everywhere else in the world you will most likely always get an offset for weather avoidance.

Yeah stinky it's one of those obscurities like the composite flight plan or even a contact approach for that matter. I think the first time I did one of those was because someone ahead of us asked for one and got it and we were like "hey I wanna try that too..."

Really? We used to do contact approaches on a daily basis. Best thing to do for all those controlled airports without ATC facilities. Contact approaches were basically permission to do whatever you wanted.

[oldtimer]

I have heard pilots requesting 1000 on top in the USA a few times but never in Canada except in the mountains so they can stay below the oxygen requirements on portions of airways. Good example is between YYC and YKA where a small portion of the airway has a MRA of 15,000 and a MOCA of 10,500ft. I have also heard pilots saying they were unable 1000 on top and required a "hard" altitude. I have never used it in all the years of IFR.
The ones I have heard using 1000 on top are usually singles or what is usually a non de-ice equipped twin. I could have used it in the King Air 100 (lower pressurization differential) but a request for a block of altitudes did the trick.
I think it is mostly an American thingee that is available in Canada but seldom used as there are other options. Higher traffic levels in the USA may not allow ATC to issue a block of altitudes.

[AuxBatOn]

I don't believe 1000 ft on top is an actual procedure in Canadian Civil Aviation.

Regardless, in the military, I use it every time there is a low to medium undercast layer. You are still technically on an IFR clearance (you receive an EAT), but are free to manoever as required. That enables us to get to the airspace more efficiently while still having the comfort of a comm fail option with undercast layer. We use it for local training only.

[CharlieMaso]

Thanks for the replies. Im pretty familiar with the rules of it (but not real life scenarios obviously) so maybe I can clear up a few misconceptions here:

1. It is an IFR procedure published in AIM available for civilian aircraft (below)
2. It is very very different to what you hear in the USA. 1000ft on top in USA is more like VFR OTT here in Canada.

Anyway - here it is, straight from the TC horses mouth:

1 000‑ft‑on‑top IFR flight may be conducted provided that
(a) the flight is made at least 1 000 ft above all cloud, haze,
smoke, or other formation;

(b) the flight visibility above the formation is at least
three miles;

(c) the top of the formation is well defined;

(d) the altitude appropriate to the direction of flight is
maintained when cruising in level flight;

(e) the “1 000‑ft‑on‑top” flight has been authorized by the
appropriate ATC unit; and

(f) the aircraft will operate within Class B airspace at or
below 12 500 ft ASL, Class C, D, or E airspace.

NOTES: ATC does not apply separation to aircraft
operating 1 000‑ft‑on‑top except in the
following conditions:
1: at night, separation is applied between an aircraft
operating 1 000‑ft‑on‑top and other aircraft if any
of the aircraft are holding; and
2: between aircraft operating 1 000‑ft‑on‑top and
an aircraft operating on an altitude reservation
approval.

[co-joe]

Yeah Joe Blow I guess the contact can be pretty useful depending on where you are. YMM, YQU, YPE that sort of thing they can be great. I always found you'd go so long without using them that you'd forget the criteria and ATC can't suggest it, so you'd hear the guy in front of you ask for one and get it...

It's like the one day a year you need to do an RVR 1200 departure and everyone in the pilots lounge has to argue about what all the rules actually are to make it happen..."...do we both have to have sim training or just me and on and on..." At least in yyc. On the coast you probably use it all the time.

[CharlieMaso]

Something i've always found interesting is the the IFR aircraft that accepts 1000ft on top looses its right to IFR separation. But the aircraft that he takes a run never said a thing about forefitting their IFR separation yet they still end up with someone whizzing by their window!!

[Wonderdog]

when you are teaching me.
SMcL.

[pilotidentity]

As separation is not provided you could request it to remain at say 9000 instead of accepting a clearance to 11000 due to traffic. Two advantages of this - if there was much stronger headwinds at the higher alt, and also the lack of the need for oxygen after half an hour above 10,000.

[pelmet]

Came across this thread in a search after looking not the subject recently.

It seems to me that a pilot might request it in order to avoid inconveniences due to separation requirements. Basically, going VFR in a situation where VFR is not allowed to allow a lesser amount of separation. There is a Visual Climb/Descent procedure as well.

My guess is that it is designed to allow some flexibility in certain situations to avoid delays.

[Fly0nTheWall]

(f) the aircraft will operate within Class B airspace at or
below 12 500 ft ASL, Class C, D, or E airspace.

Genuine question, where would you be in Class B airspace below 12 500 ft ASL? Sounds like a weird clause to add in there.

[Scuderia]

(f) the aircraft will operate within Class B airspace at or
below 12 500 ft ASL, Class C, D, or E airspace.

Genuine question, where would you be in Class B airspace below 12 500 ft ASL? Sounds like a weird clause to add in there.

While one does not exist (as far as I know), the DAH could technically designate a control zone or area as Class B as well.

[Fly0nTheWall]

(f) the aircraft will operate within Class B airspace at or
below 12 500 ft ASL, Class C, D, or E airspace.

Genuine question, where would you be in Class B airspace below 12 500 ft ASL? Sounds like a weird clause to add in there.

While one does not exist (as far as I know), the DAH could technically designate a control zone or area as Class B as well.

Ah ok, interesting.