Need desperate help with diversions!

captainphil

Well-Known Member
I am scheduled tommorrow for a stage check for the end of stage 2. I do my maneveurs fine but the one thing I am terrible at is diversions. It's mostly trying to do the math estimations that gets me. Sure I could use an E6b but he wants to be able to do it in my head if I ever need it.

I was wondering if any of you guys/girls had a simple way of breaking down the math in my head. I am using 75% power and burning 11.4 GPH and what they want me to find is:

an estimated heading to get to a new airport

ground speed

how many miles ( for this I look at the runway and say to myself it looks a mile long and I imagine stacking those runways toward my plane to estimate how many miles, is that ok ?) I know I could use my sectional but again, he wants me doing this without help.

how much fuel burn ( This is what I need the most help on)

and ETE to new airport

Please help! thanks.
 

sorrygottarunway

Well-Known Member
I would first start by looking at your map and picking a suitable alternate. Since hopefully you know your position already on that map, you can make a generalized turn towards the airport. Now, along the way you can start the calculations...

I guess if he just wants you to use your head and no other fancy instruments, try this:

Take a piece of paper and put it along an imaginary course line from your present position to your diversion airport. Then place a hatch mark at your present position and one at your diversion airport. This will get your distance. Then bring that paper over to any VOR rose printed on the map. This will get your magnetic heading, uncorrected for winds. Knowing the winds, this will help you correct the head you're flying for more precision. You can now take that paper and bring it down to the legend where you will find the NM scale and use it to find the approximate distance. Lets say its 50NM. Also, lets say that your flight-plan calculated ground speed was 130 knots, and now this turn takes you away from some of your tailwind component (or makes your headwind component increase...). You think you'll loose about 5-7kts of ground speed, but lets be conservative and say 10 knots. Now you estimate your groundspeed at 120 knots.

You know in your head that 120kts is about 2 miles per minute ((120 kts/hr)/60 mins)=2 NM/min, so you'll be traversing that 50 NM in about 25 minutes to the alternate.

Just shy of half an hour right? So take your GPH flow, and just shy of half would be 5.6 gallons.

You've found time, distance, and fuel consumption to your alternate.

Its no FMS solution, but it will get the job done.
 

wheelsup

Well-Known Member
They want you to find the distance in your head? By looking outside? Really? That's a very unrealistic expectation. I've worked at numerous flight schools and none wanted any of that done in your head, or required it. Use an E6B (manual kind). Maybe you don't fully understand what they are looking for (not trying to be a jerk, ie could just be mis-communication).

Your school should have some form of ops manual or "how to" section that should walk your thru it, how to do it, and whats expected. Most do, especially if you're doing stage checks, sounds like an organized 141 FBO.
 

PGT

Well-Known Member
120 knots = 2nm/min
90 knots = 1.5nm/min

I would:

miles from airport / nm a minute = how many minutes til you get there

I would round the GPH up to 12, easier to do math that way. If it takes you 10 minutes to reach the airport then> 10minutes = 1/6th of 60min. so whats 1/6th of 12gallons? 2 gallons.
 

bdhill1979

Gone West
Suggestions:

The approximate heading is just that, an approximation. If the airport is northwest of you turning to a heading of 315 is just fine. Once heading in the general direction you can work on picking out landmarks for better navigation.

Determine now how much distance parts of your body cover on a sectional chart. The end of my thumb is about 10 miles, if I spread my hand the tip of my thumb to the tip of my pinky is about 65 miles. Thus approximate distance estimates are quick and easy.

Then for time and fuel burn just use rule of thumb calculations. the average single engine trainer will cover about 2 miles per minute at cruise, at 12 gallons per hour you are burning a gallon every 5 minutes.

Figuring those things out now will make future calculations really quick an easy.
 

captainphil

Well-Known Member
They want you to find the distance in your head? By looking outside? Really? That's a very unrealistic expectation. I've worked at numerous flight schools and none wanted any of that done in your head, or required it. Use an E6B (manual kind). Maybe you don't fully understand what they are looking for (not trying to be a jerk, ie could just be mis-communication).

Your school should have some form of ops manual or "how to" section that should walk your thru it, how to do it, and whats expected. Most do, especially if you're doing stage checks, sounds like an organized 141 FBO.
Yes it's 141, and the manual does explain it, but it doesn't go over the math.And no your not being a jerk, your being helpful and I appreciate it.
 

captainphil

Well-Known Member
Thank you all so much for your help, this makes it so much more understandable. Thank god (doug taylor)for this forum :laff:.
 

wheelsup

Well-Known Member
If they let you use a sectional, the easiest way to find a heading IMO is use a pencil/plotter and place it from your a/c position to the destination to get the angle, then slide it over the center of a VOR compass rose, presto instant Mag heading, add a few degrees for wind correction and you're done.

It probably doesn't go over the math because 99.9999999% of the people out there use an E6B, I've personally never met anyone or flown with anyone who wanted it done in my head.
 

captainphil

Well-Known Member
If they let you use a sectional, the easiest way to find a heading IMO is use a pencil/plotter and place it from your a/c position to the destination to get the angle, then slide it over the center of a VOR compass rose, presto instant Mag heading, add a few degrees for wind correction and you're done.

It probably doesn't go over the math because 99.9999999% of the people out there use an E6B, I've personally never met anyone or flown with anyone who wanted it done in my head.
In your opinion, do you think it might help me become a better pilot doing it mentally, Im very bad at mental math.
 

sorrygottarunway

Well-Known Member
In your opinion, do you think it might help me become a better pilot doing it mentally, Im very bad at mental math.
I'm probably one of the few instructors out there that thinks that any detailed math other than basic rule-of-thumb equations is a bad idea (unless you have gadgetry helping you out) in the cockpit! I'm awful at math, but I still made it through :)
 

bdhill1979

Gone West
I'm probably one of the few instructors out there that thinks that any detailed math other than basic rule-of-thumb equations is a bad idea (unless you have gadgetry helping you out) in the cockpit! I'm awful at math, but I still made it through :)
:yeahthat:

My famous saying is:
If you are doing math in the cockpit you are doing something wrong
 

wheelsup

Well-Known Member
I'd say simple mental math would definitely help. I personally like to do the ol' 3:1 calculation and throw that up on the FMS to give myself an idea of when to start the TOD if ATC wants me to make a crossing restriction, for instance. And ground speed x 6 gives you a 3:1 decent rate. All useful.
 

Number1atNumber2

Tries to keep it fun.
I'm god aweful at math as well, one thing that helps me is don't be afraid to round numbers up/down to make the math easier. ie you're doing 115 knts, round it up to 120, then you know you're doing 2 miles a min. 11.4 gal per hour, round up to 12. So long as you aren't calculating over long distances, it shouldn't hurt you that bad.

Save the exact planning for when you're not in the plane. Best thing I heard from an instructor on the subject of cross countries: "We look at it under a microscope, measure it with a micrometer, then cut it with an axe."
 

milleR

Well-Known Member
Take a wooden pencil and lay it alongside your plotter. Line up the end of the metal part of the eraser with the 0 and take a Bic pen and place marks for every ten miles.

When you're asked to divert take the pencil and lay it from you position to the closest suitable apt. You can now estimate the distance and direction, which means you know the eta. If fuel burn is a problem you chose the wrong field so don't worry about it. All the examiner wants to know is a heading, distance, and time enroute.
 

milleR

Well-Known Member
how many miles ( for this I look at the runway and say to myself it looks a mile long and I imagine stacking those runways toward my plane to estimate how many miles, is that ok ?) I know I could use my sectional but again, he wants me doing this without help.
This isn't a diversion. If you've already selected a field there shouldn't be much planning involved if you can see it. Maybe they're asking if you could make the field without power?
 

captainphil

Well-Known Member
This isn't a diversion. If you've already selected a field there shouldn't be much planning involved if you can see it. Maybe they're asking if you could make the field without power?
They want me to know if I have enough fuel to get there, about how long it will take, estimate how much ill burn.
 

milleR

Well-Known Member
They want me to know if I have enough fuel to get there, about how long it will take, estimate how much ill burn.
Then based on what you said before, if you can see the field why is fuel burn an issue? If the engine is running you can make it, if not it's a different issue. Otherwise use whichever system has been recomended here that best suits you.

It's all about approximation, so long as you show the examiner that you know where you're going to go (if you're familiar with the area then you already know), how you're going to get there (you can fly the airplane so don't worry about it) and how long it will take (basic math using the ol' pencil trick) you'll be fine.

All the examiner wants to see is situational awareness.
 

HOTDOG

New Member
Suggestions:

The approximate heading is just that, an approximation. If the airport is northwest of you turning to a heading of 315 is just fine. Once heading in the general direction you can work on picking out landmarks for better navigation.

Determine now how much distance parts of your body cover on a sectional chart. The end of my thumb is about 10 miles, if I spread my hand the tip of my thumb to the tip of my pinky is about 65 miles. Thus approximate distance estimates are quick and easy.

Then for time and fuel burn just use rule of thumb calculations. the average single engine trainer will cover about 2 miles per minute at cruise, at 12 gallons per hour you are burning a gallon every 5 minutes.

Figuring those things out now will make future calculations really quick an easy.
This is similar to the way I was taught to do it when I took my private pilot check ride back in '01.
 

Stomp16

You mean Shennanigans?!?!
Don't rush! If you rush your gonna make an error. As soon as they say divert, find the closest airport and turn towards it. Note the time when you begin the turn. Once you are stabilized and on course, then start figuring time, distance and fuel burn. The mental math to do this is VERY simple, even if you say your bad at it. After a couple times of doing diversions, it will become second nature. Above all else though, don't rush through the diversion. Get out your plotter, E6B (and a calculator if you need it). Take it slow and you'll be fine.

BTW, if you use your E6B to find your wind correction heading, they really like that. It show's you pay attention to details.
 

PGT

Well-Known Member
BTW, if you use your E6B to find your wind correction heading, they really like that. It show's you pay attention to details.
I would be careful with this one, some might see it as a bad thing i.e you are diverting for a reason and should focus on flying the plane and not having your head down
 
Top