Filing highest altitude with icing

[TuomoMooneyFlying]

Wondering what’s the preferred way to file? I was always told to file for the highest cruising altitude but it looks like that would route me through icing. If I waited for about 75nm lower, then I could climb beyond the forecasted icing area. So should I file lower, then ask for higher or file for higher and then ask to stay lower until past the forecasted icing area?

 

[Hypie]

Wondering what’s the preferred way to file? I was always told to file for the highest cruising altitude but it looks like that would route me through icing. If I waited for about 75nm lower, then I could climb beyond the forecasted icing area. So should I file lower, then ask for higher or file for higher and then ask to stay lower until past the forecasted icing area?

I always file for lower then ask ATC for higher when I need it, seems to lessen the confusion.

 

[Rick A]

If the ground temps in that section of your flight are less than 40 degrees F don't be inside the clouds, only below. If terrain, obstacles, visibility and cloud bases permit fly VFR and stay low. Even if it means cancelling your IFR and descending. Always leave yourself an out.

Consider picking up more than a dusting of ice with the same urgency as fire. If IFR and picking up ice and ATC isn't willing to give you an altitude change immediately upon you requesting an altitude change due to ice, declare an emergency and do what you have to do to get out of it. And make sure the ground OAT's are 40F or higher.

 

[Roger Wilco]

Generally, I would suggest filing for what you want or intend. Do you want or intend to fly in forecast icing conditions? If no, then don't file for a cruise altitude that will expose you to potential icing. See 91.527 91.9a. In addition, consider your predicament if you were to lose ATC comms while encountering actual icing conditions. See 91.185.

Once underway, you can always request a cruise altitude different from filed. But any attempt at flying a light single(!) in IMC when potential icing conditions exist anywhere along the route should be very carefully considered, and there's a lot to be considered. I suggest that the first thing to consider is staying on the ground or flying commercial.

 

[Martin Pauly]

Wondering what’s the preferred way to file? I was always told to file for the highest cruising altitude but it looks like that would route me through icing. If I waited for about 75nm lower, then I could climb beyond the forecasted icing area. So should I file lower, then ask for higher or file for higher and then ask to stay lower until past the forecasted icing area?

I file my initial altitude in the flight plan, then request changes with ATC in the air. That avoids extra communication and potential confusion early in the flight when things are busy.

- Martin

 

[midlifeflyer]

I file my initial altitude in the flight plan, then request changes with ATC in the air. That avoids extra communication and potential confusion early in the flight when things are busy.

- Martin

This. The altitude you enter into the flight plan should be the cruising altitude you want to start with. Modifications happen all the time. Some initiated by the pilot (icing, clouds, turbulence for example). Others initiated by ATC (direction of flight; traffic considerations). I think that may have been clearer in FAA publications at one time.

 

[TuomoMooneyFlying]

I file my initial altitude in the flight plan, then request changes with ATC in the air. That avoids extra communication and potential confusion early in the flight when things are busy.

- Martin

Perfect, thank you Martin!

 

[Rick A]

Perfect, thank you Martin!

And when the controller says "no" to a requested altitude change, let the negotiations begin!! Always remembering the controller is safely on the ground sitting in a comfortable chair, and you're not.

 

[Doc Holliday]

Generally, I would suggest filing for what you want or intend. Do you want or intend to fly in forecast icing conditions? If no, then don't file for a cruise altitude that will expose you to potential icing. See 91.527.

Why would he be concerned about regulations concerning Large Turbine Powered aircraft and 91k?

91.527 falls under subpart F

Subpart F

Large and Turbine-Powered Multiengine Airplanes and Fractional Ownership Program Aircraft

§ 91.501 Applicability.​

(a) This subpart prescribes operating rules, in addition to those prescribed in other subparts of this part, governing the operation of large airplanes of U.S. registry, turbojet-powered multiengine civil airplanes of U.S. registry, and fractional ownership program aircraft of U.S. registry that are operating under subpart K of this part in operations not involving common carriage. The operating rules in this subpart do not apply to those aircraft when they are required to be operated under parts 121, 125, 129, 135, and 137 of this chapter. (Section 91.409 prescribes an inspection program for large and for turbine-powered (turbojet and turboprop) multiengine airplanes and turbine-powered rotorcraft of U.S. registry when they are operated under this part or part 129 or 137.)

 

[WDD]

In this situation, the best way to file would be for 24 hours or whatever later so you don't deal with icing.

 

[Roger Wilco]

91.527 falls under subpart F

That is correct--I'm getting too careless. For the purposes of the OP, the most relevant reg would probably be 91.9a.

 

[MRC01]

I file my initial altitude in the flight plan, then request changes with ATC in the air. That avoids extra communication and potential confusion early in the flight when things are busy.

This. The altitude you enter into the flight plan should be the cruising altitude you want to start with. Modifications happen all the time. Some initiated by the pilot (icing, clouds, turbulence for example). Others initiated by ATC (direction of flight; traffic considerations). I think that may have been clearer in FAA publications at one time.

Yep, it's straight from IFR ground school and one of the test questions. Q: what do you enter into box 15 "Level" of the flight plan? A: Initial cruising altitude. That doesn't always mean it's how it should always be done in the real world, but it's good to know.

 

[Roger Wilco]

Wondering what’s the preferred way to file?

After giving this a bit more thought (and less concern about the prospect of encountering icing conditions in your Mooney), I suggest that the best way to file is to enter your desired initial cruise altitude in the LEVEL block, and include desired changes in the ROUTE block, i.e. DCT AHN T224 ELW/N0150A090. As I and others have previously stated, you can request an altitude change anytime.

 

[midlifeflyer]

Yep, it's straight from IFR ground school and one of the test questions. Q: what do you enter into box 15 "Level" of the flight plan? A: Initial cruising altitude. That doesn't always mean it's how it should always be done in the real world, but it's good to know.

There are always exceptions. But I figure it this way. The clearance one gets is likely to include, "climb and maintain X,000. Expect [filed altitude] 10 minutes after departure," about 90% of the time unless ATC traffic considerations delay it. I also suspect it's going to be far easier get a change down the line than than during the departure phase that's busy for both.

 

[midlifeflyer]

After giving this a bit more thought (and less concern about the prospect of encountering icing conditions in your Mooney), I suggest that the best way to file is to enter your desired initial cruise altitude in the LEVEL block, and include desired changes in the route block, i.e. DCT AHN T224 ELW/N0150A090. As I and others have previously stated, you can request an altitude change anytime.

Do you know: does ATC even see those requested changes? Or understand them if they do?

 

[TCABM]

Do you know: does ATC even see those requested changes? Or understand them if they do?

In the last quarter or so, Opposing Bases covered what happens between filing and issuance and the answer is it depends.

 

[midlifeflyer]

In the last quarter or so, Opposing Bases covered what happens between filing and issuance and the answer is it depends.

They've talked about comments a few times. The overall impression I got was that seeing it at all depends on a combination of size of the comment field and the facility's tech.

I'm used to short items like IFR TRNG or LUV ATC or, their favorite, a contact phone number, being caught, so I wondered a little about the 26 characters in this one.

But I wondered a lot more about whether, if it were seen, a controller would even understand "DCT AHN T224 ELW/N0150A090" as a requested change to 9,000' at ELW VOR (at a cruise airspeed of 150 KIAS). Or, if understood, would make any difference in the way they handled the flight. There's quite a bit of stuff in the ICAO flight plan that has relevance in other countries but little to none in the US NAS.

 

[Martin Pauly]

There's quite a bit of stuff in the ICAO flight plan that has relevance in other countries but little to none in the US NAS.

That's true. I remember from my flying days in Europe (three decades ago) that these planned altitude changes (while enroute) were somewhat common in IFR flight plans.

I have never tried to utilize it in the US. Why would I? From a practical perspective, even if I anticipate wanting an altitude change sometime during the flight, I like that I can leave the details (exact time/location, what new altitude to climb/descend to) open until I get there. That way, I can take the actual conditions I face (clouds, winds, turbulence, icing, etc.) at the time of my flight into consideration, at least in US airspace. Other regions may not offer so much flexibility.

- Martin

 

[Roger Wilco]

Do you know: does ATC even see those requested changes? Or understand them if they do?

Are any ATC types still active here? They would be the best people to ask. From the cockpit side of the system, I'd answer yes to both questions.

They've talked about comments a few times. The overall impression I got was that seeing it at all depends on a combination of size of the comment field and the facility's tech.

By "comments," do you mean remarks? Speed and altitude/level changes should be entered in the route block.

I'm used to short items like IFR TRNG or LUV ATC or, their favorite, a contact phone number, being caught, so I wondered a little about the 26 characters in this one.

But I wondered a lot more about whether, if it were seen, a controller would even understand "DCT AHN T224 ELW/N0150A090" as a requested change to 9,000' at ELW VOR (at a cruise airspeed of 150 KIAS). Or, if understood, would make any difference in the way they handled the flight. There's quite a bit of stuff in the ICAO flight plan that has relevance in other countries but little to none in the US NAS.

Certainly the controller would understand a filed route. Whether or not ATC working the flight would notice the requested climb would probably be up to the individual and his/her workload. But apropos the OP, I suggest that this is the "preferred way to file."

 

[TCABM]

They've talked about comments a few times. The overall impression I got was that seeing it at all depends on a combination of size of the comment field and the facility's tech.

I'm used to short items like IFR TRNG or LUV ATC or, their favorite, a contact phone number, being caught, so I wondered a little about the 26 characters in this one.

But I wondered a lot more about whether, if it were seen, a controller would even understand "DCT AHN T224 ELW/N0150A090" as a requested change to 9,000' at ELW VOR (at a cruise airspeed of 150 KIAS). Or, if understood, would make any difference in the way they handled the flight. There's quite a bit of stuff in the ICAO flight plan that has relevance in other countries but little to none in the US NAS.

Comments section vs the route field are two different things, I think.

The gist of conversation was if your EFB-planned & filed route was submitted >45 mins before takeoff, it goes thru flight data and may be auto-/computer routed and potentially human modified. However if it’s submitted or changed w departure facility gives you, despite what you communicate in the routing.

I believe comments are not transmitted or displayed/printed at the departure facility. It’s been a moment since I listened to the podcast, but I’ll see if I can dig it up as I found it quite informative.

ETA: from OB398

SHOW TOPIC: THE FLIGHT PLAN MIX-UP (21:07 – 42:34)
Sponsored by Emperor Captain November Sierra
What happens when you cancel and refile an IFR flight plan too close to your scheduled departure? One listener’s experience exposes a procedural blind spot.

• Context:

Departing near the Sourdough Bravo.

Files a route inland to stay within gliding distance but accidentally leaves the altitude at 11,000, triggering an offshore route.

Tries to fix it last-minute—cancels and refiles with the correct altitude and desired routing.

• The Mix-Up:

ATC issues a clearance for the first flight plan (offshore), not the corrected second one.

Because the first fix was identical, the discrepancy wasn’t obvious until enroute.

The climb to 9,000 instead of 7,000 raised red flags for the pilot, who asked what route ATC had.

Realized the offshore route was being used. Thankfully, the controller was able to fix it.

• AG’s Analysis:

Flight plans filed within 30 minutes can print immediately to a controller.

Canceled flight plans may not auto-remove from the system, especially if initiated by the pilot’s EFB.

Controllers may miss that a second flight plan exists, especially under pressure.

• Best Practices for Pilots:

File flight plans early—well outside the 30-minute departure window.

If you must cancel and refile close to departure, confirm ATC is issuing clearance from the second plan.

Use the remarks section—“amended altitude” or “FRC” can signal a change to controllers.

If suspicious, initiate a full route clearance request. Don’t assume “as filed” means what you think it does.

Understand that crossing flight plans can cause chaos behind the scenes with transponder codes and strip data.

• RH's Summary:

The controller may never know a second flight plan exists.

If you're issued something different than expected—especially altitudes or airspace—you must speak up.

Excellent catch by the listener.

 

[Roger Wilco]

That's true. I remember from my flying days in Europe (three decades ago) that these planned altitude changes (while enroute) were somewhat common in IFR flight plans.

I have never tried to utilize it in the US. Why would I? From a practical perspective, even if I anticipate wanting an altitude change sometime during the flight, I like that I can leave the details (exact time/location, what new altitude to climb/descend to) open until I get there.

I'd guess that's how the vast majority of us do it.

That way, I can take the actual conditions I face (clouds, winds, turbulence, icing, etc.) at the time of my flight into consideration...

Yes, and that option is available regardless of how we file.

 

[midlifeflyer]

Certainly the controller would understand a filed route. Whether or not ATC working the flight would notice the requested climb would probably be up to the individual and his/her workload."

Thanks. I agree that this is part of the filed "route," not just a bunch of comments.

But apropos the OP, I suggest that this is the "preferred way to file.

We can disagree on that part. "A" way to file doesn't automatically mean it's preferred. If there was that much benefit, it would be done a lot. I wonder how many here even understood that notation.

I can imagine a benefit in an environment where two-way communications are spotty, or where it's in common usage. But in the US NAS, from a strictly practical standpoint, where we have widespread radar and communications, it simply doesn't provide any benefit.

 

[Roger Wilco]

We can disagree on that part. "A" way to file doesn't automatically mean it's preferred. If there was that much benefit, it would be done a lot. I wonder how many here even understood that notation.

I agree with your disagreement, with the understanding that the OP was a solicitation of input from others. That's why I used the word "suggest" to indicate that my response was just one opinion.

I can imagine a benefit in an environment where two-way communications are spotty, or where it's in common usage. But in the US NAS, from a strictly practical standpoint, where we have widespread radar and communications, it simply doesn't provide any benefit.

Again, here's where some input from actual ATC folks would help. I cannot argue that there is, or that there is not, any practical benefit to including speed and altitude changes in the FP, only that the ability to do so exists. I know of at least one large airline that does, in fact, designate speed and altitude changes in the filed domestic route, and it's reasonable to assume that others do also. This may be solely because the system is programmed to transmit the same format for domestic and international operations.

 

[flyingcheesehead]

File the *initial* cruising altitude, request changes later.

This. The altitude you enter into the flight plan should be the cruising altitude you want to start with. Modifications happen all the time. Some initiated by the pilot (icing, clouds, turbulence for example). Others initiated by ATC (direction of flight; traffic considerations). I think that may have been clearer in FAA publications at one time.

Yes! I remember that when I was learning to fly it was very clear that this was to be the initial cruising altitude, but I believe that was in the instructions for the FAA Flight Plan Form. Now that they switched to ICAO, it no longer explicitly specifies that, but I think that was an oversight.

After giving this a bit more thought (and less concern about the prospect of encountering icing conditions in your Mooney), I suggest that the best way to file is to enter your desired initial cruise altitude in the LEVEL block, and include desired changes in the ROUTE block, i.e. DCT AHN T224 ELW/N0150A090. As I and others have previously stated, you can request an altitude change anytime.

Do you know: does ATC even see those requested changes? Or understand them if they do?

Per the AIM, Appendix 4, f.5.(c), no:

(c) It is acceptable to specify intended speed and altitude changes along the route by appending an oblique stroke followed by the next speed and altitude. However, note that FAA ATC systems will neither process this information nor display it to ATC personnel. Pilots are expected to maintain the last assigned altitude and request revised altitude clearances from ATC.​

 

[midlifeflyer]

Per the AIM, Appendix 4, f.5.(c), no:

(c) It is acceptable to specify intended speed and altitude changes along the route by appending an oblique stroke followed by the next speed and altitude. However, note that FAA ATC systems will neither process this information nor display it to ATC personnel. Pilots are expected to maintain the last assigned altitude and request revised altitude clearances from ATC.

Nice job!

 

[Roger Wilco]

File the *initial* cruising altitude, request changes later.


Yes! I remember that when I was learning to fly it was very clear that this was to be the initial cruising altitude, but I believe that was in the instructions for the FAA Flight Plan Form. Now that they switched to ICAO, it no longer explicitly specifies that, but I think that was an oversight.



Per the AIM, Appendix 4, f.5.(c), no:

(c) It is acceptable to specify intended speed and altitude changes along the route by appending an oblique stroke followed by the next speed and altitude. However, note that FAA ATC systems will neither process this information nor display it to ATC personnel. Pilots are expected to maintain the last assigned altitude and request revised altitude clearances from ATC.​

There it is! Thanks for finding that reference.