Do you compensate somehow for the time it takes to fly an approach when filing IFR with Foreflight?
Posted by andybader@reddit | flying | View on Reddit | 42 comments
I'm preparing for my instrument checkride and I'm trying to apply all the theory I'm learning to the real world. One thing I'm considering is IFR flight plan ETA.
Generally, I assume I'll be filing to an airport and not including any procedure in my flight plan (because ATC doesn't want it and because I won't know the runway in use). Foreflight calculates my ETA based on the legs I enter into the flight plan. If I consider having to fly a full procedure, it might add ten minutes to my flight.
Do you make any adjustments for this, or does it not really matter? Does ETA only matter for lost comms? Do you add a few minutes and a gallon of fuel in your head?
anactualspacecadet@reddit
Foreflight will build in the time it takes to do the approach if you tell it what you’re gonna do, if you ask me this is pretty useless because really you’re gonna do whatever approach control wants
andybader@reddit (OP)
That's what I've been thinking. Just so I could learn the difference, I saved two flights: from the last real waypoint to the airport, and from the last real waypoint to every point in the approach I'm expecting. Nine minutes difference.
When I file IFR for real I'll be doing the former.
anactualspacecadet@reddit
What speed do you fly approaches at? In usaf we generally do fuel burn at average approach speed for 15 minutes to calculate gas for penetration and approach
andybader@reddit (OP)
I’m in a C172, so on the approach course I’m usually descending at 85 kts and 1700 rpm.
It’s probably a good idea to crack open the POH and see what that actually comes out to, but I think adding ten minutes of cruise fuel burn is probably easier and more conservative.
anactualspacecadet@reddit
Thats probably a pretty safe estimate, although for some longer arcing approaches you might be more right to shoot for 15 minutes, what speed do you cruise at? Like 110?
andybader@reddit (OP)
Pretty close. 107 KIAS, so 110 is probably a good estimate at any given altitude.
anactualspacecadet@reddit
I mean is it so hard to just figure out the fuel burn for 15 minutes at 1700 rpm lol, i would just do that in your shoes, theres probably a chart somewhere with that number
andybader@reddit (OP)
Haha, not hard at all and yes I have the charts. I’m more asking: does anybody actually go to the trouble to do this. Considering it as part of the 45 minute IFR reserve seems very reasonable (especially since I have a higher personal minimum).
anactualspacecadet@reddit
Is it 45 minutes for every flight? We have some kind of waiver cuz we don’t always have that. Our reserves is 20 minutes minimum up to 45 minutes or 10% of your flight time, you’re not supposed to use that gas to do your intended approach tho
andybader@reddit (OP)
Oh, interesting. Yup, for every flight. VFR you must have enough fuel to arrive at your destination and then fly at normal cruise for 30 minutes. IFF it’s to your destination, then alternate if required, then 45 minutes at normal cruise.
anactualspacecadet@reddit
Yeah so my understanding is you shouldn’t be using your reserves for your intended approach, or at least that shouldn’t be your plan
DanThePilot_Man@reddit
This is correct. The regulation states you may not OPERATE under IFR unless you carry an extra 45 minutes of gas. This does not refer to taking off. If you are in flight and you dip into your 45 minutes, the regulation is now being broken.
gbchaosmaster@reddit
This isn't true. The regulation is for planning only; if you plan the flight and competently calculate that you'll have the legal fuel reserve, but you end up dipping into that reserve, you're perfectly legal. The whole reason for planning a reserve is so you can use it if you need it.
91.167 also doesn't specify the need to plan for shooting the approach, it's probably a good idea to, but you're still legal even if you know the IAP would put you below minimums. The letter of the law states you only need to be able to fly to the destination, then to the alternate (if required) with 45m reserve.
DanThePilot_Man@reddit
Are you interpreting that to mean a direct route to destination? If so I believe your interpretation is flawed.
gbchaosmaster@reddit
No, via filed route.
DanThePilot_Man@reddit
https://drs.faa.gov/browse/excelExternalWindow/FAA000000000LEGALINTPR2006011PDF.0001?modalOpened=true
See this LOI and tell me if you still think you dont need to plan for the approach. 91.13 is quite likely to apply if you dont.
gbchaosmaster@reddit
Got me! I love me a good legal interpretation, adding this one to the bookmarks.
anactualspacecadet@reddit
But you guys really fly with 45 mins of gas every time you file IFR? What if its a 45 minute flight?
DanThePilot_Man@reddit
Yes, you take off with gas to destination + gas to alternate + 45minutds.
anactualspacecadet@reddit
Do you know if airlines do that too? I only ask because 45 minutes of gas in like a 787 is a LOT of gas
SirKillalot@reddit
It's a lot of gas but it's not that much relative to the all-up weight of the 787 - the amount you burn to fly for 3 hours while carrying 3h45 of fuel is not that different from the amount you burn to fly 3 hours carrying 3h00 of fuel, and stretching those aircraft to the limits of their endurance is pretty rare.
I think fighter aircraft are likely to have more trouble with this than airliners due to carrying more weight of fuel and burning it faster relative to their total weight.
It does become a little bit of a problem for me in my little two-seat bugsmasher. With full tanks it has about 4.5 hours of fuel burn, so my IFR endurance is limited to 3h45. That's probably about as long as I want to fly in it in one sitting anyway, especially in weather. But I'm a bigger guy, and I often need to cut into my fuel load to take a passenger. If I can only take off with 3 hours of fuel then cutting it down to 2h15 does limit my options a lot more, especially if I need an alternate.
I imagine fighters face the same thing trying to stretch their endurance, but you have a) the ability to divert a lot further in the same amount of time than I do, although your choices of alternates are probably limited to longer runways and b) some level of priority handling from ATC - from what I've heard they broadly understand your constraints and generally give you direct routings and no delays, though I don't know of any official policy to that effect.
anactualspacecadet@reddit
Fighters do this cool thing where they connect to another airplane and get more gas. With enough dextroamphetamine there’s no reason you couldn’t fly for like 3 days straight
DanThePilot_Man@reddit
According to 121.639, yes they would be required to do that. But I suspect maybe there are opspecs that allow for less. Really I have no idea, but the reg says it’s required.
dieseltaco@reddit
penetration
anactualspacecadet@reddit
Yes:)
rdrcrmatt@reddit
I’ve found adding 15 minutes per approach is usually a pretty close guess.
saml01@reddit
I include extra fuel for a missed. The other differences are made up by the reserve.
VileInventor@reddit
ForeFlight that shit and forget about it
sirduckbert@reddit
In my head I have the number for hold, approach, and min landing fuel, plus fuel for start taxi and takeoff. Add that to the number foreflight gives you. If it’s a checkride, do a paper navlog to show your work clearly - then they won’t ask as many questions
MontgomeryEagle@reddit
I nearly always fly IFR, I nearly always beat the flight time Garmin Pilot calculates. The apps don't give you credit for faster descents, which is usually a thing in a piston airplane.
forseth11@reddit
Those saying it doesn't matter are likely flying jets and going straight in.
See how long it takes you to fly an approach on average, then add that to your calculation.
Consider a C150 with two VORs and a DME. Without vectors (always plan without vectors in case), you may need to fly 30nm to a VOR for an IAF. Then fly another 30nm for the full procedure. From that IAF and assuming no procedure turn, 30nm in a 150 will take you 22 minutes. That's quite a lot more than just doing a straight in.
The same goes for more complex procedures. Consider the KGJT LDA 29. Mountains may require the full procedure. JNC to SPADA on the arc is 21 miles. Then you gotta fly the arc. Then fly another 12nm final. Flying this in a Mooney at 145kts would take about 18 minutes. Not bad, but definitely not negligible. Not to mention if going missed, you gotta go all the way back to JNC and do it over again.
Low_Sky_49@reddit
It doesn’t factor into my ETA. I file to the destination airport and let the chips fall where they may with the approach. For fuel planning, I pick the worst case scenario approach for the destination and alternate if required and let ForeFlight do the math (with vetted performance profiles).
Mispelled-This@reddit
I didn’t think to do this on my checkride, and the DPE didn’t say anything either.
In the real world, you’re usually going to get vectored for a visual approach, and good luck calculating the time or fuel for that. Getting randomly pushed down low 50+ miles out will hurt you far more than an approach will anyway.
Plastic_Brick_1060@reddit
You should definitely have a good idea of the runway in use. If it's unclear which will be in use, plan your fuel on the most conservative procedure. Using an IAF as a last waypoint is a good enough estimate for fuel/time while giving a good clue to ATC what approach you're planning/expecting.
To be transparent, this is my strategy that I find works in my world that may not please every examiner and I'm sure many would disagree with me. I've never instructed and only flown jets for the past 15 years. Good luck with your ride
x4457@reddit
No
It does not
Yes
Sure, that sounds reasonable. Call it 1.5 gallons per approach in a trainer.
andybader@reddit (OP)
Sweet, thank you. I'll add it to the list of little discrepancies I'll try to explain to my DPE.
thommycaldwell@reddit
Don’t explain it unless they ask
andybader@reddit (OP)
my first instructor said "If your DPE asks you know what time it is, you just say 'yes'." I'll be following this advice.
thommycaldwell@reddit
Exactly. Never waste a good opportunity to stop talking
FlyingLongHorns1@reddit
I usually added 10 minutes per approach
100LLgatorade@reddit
Real world I don’t worry about it
Checkride I probably wouldn’t worry about it either
rFlyingTower@reddit
This is a copy of the original post body for posterity:
I'm preparing for my instrument checkride and I'm trying to apply all the theory I'm learning to the real world. One thing I'm considering is IFR flight plan ETA.
Generally, I assume I'll be filing to an airport and not including any procedure in my flight plan (because ATC doesn't want it and because I won't know the runway in use). Foreflight calculates my ETA based on the legs I enter into the flight plan. If I consider having to fly a full procedure, it might add ten minutes to my flight.
Do you make any adjustments for this, or does it not really matter? Does ETA only matter for lost comms? Do you add a few minutes and a gallon of fuel in your head?
Please downvote this comment until it collapses.
I am a bot, and this action was performed automatically. If you have any questions, please contact the mods of this subreddit.