Military climbing procedure
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Sooo… long time ago, I started with C++ and this long forgotten project popped up again.
Had some real life stuff going on in the meantime, and boy… Seeing your old code from your first C++ project ever is some strange experience :behindsofa:
It didn’t find that much interest since it was created, but it might be worth sharing it.Anway, here is a onedrive link to the program and its source code:
https://1drv.ms/f/s!AqvKZ8hkqBzhgQakPgqFLrU0iD9TIt is based on Qt, don’t judge the UI tho since it was my first C++ / Qt project ever and the UI is basically just the wrapper for testing the math code from my first steps in C++. But… this will tell you
- How much fuel you will need
- How much of your available performance you will need
- Your maximum sustained turn and rate 1 turn based on your loadout at that waypoint
- Your AOA, fuel flow, playtime
And it will do so for each waypoint.
So basically it tells you about your fuel needed for the trip (including the fuel spend on climbing) based on your drag index and fuel left at that specific waypoint. All of the data is calculated based on the selected waypoint, with that loadout, that weight (including the fuel spent), that drag index on that altitude at that speed.
The drag index can be changed for each waypoint (for example if you use ordnance) so you can even calculate how much fuel you will need for your trip back, which will take the fuel spent on your journey into account.
You can create a basic flight from a template, but you can’t save a loadout / flight yet. Sorry for that.
You can select all F-16 variants (I think) but the code is open if you want to add any HFFM models (only those are supported).
If you want to compile it by yourself:- Install Qt with the Qt creator
- Open the Qt project
- compile.
I used MinGW. Minimum Qt should be 5.6 or so while i compiled it with 5.11.2. Feel free to use the code in any of your own projects. Cleaning it up is recommened tho, I’d not use a singleton nowadays for example.
But: It works and on some tests flights, the numbers given seem to be accurate so the basic math behind it seems to be alright.
The RPM’s are given in % of the actual “load” with “0” being idle, “100” being MIL and “103” being full AB. That will deviate from the RPM display in the sim.
But adjust to that fuel flow, and you will have the same speed if you did use the right drag index, weight and fuel.A few words for using it:
- When you start it, you will have to specify the Data directory of BMS, usually this will be C:\Falcon BMS 4.34\Data. No calculations will be made without the HFFM files in that directory.
- The weight you enter is the weight of your weapons excluding fuel!
- Fuel is taken into account separately.
- Remember that everything on the right side depends on which waypoint is selected in the tree on the left side.
Have fun, report back is something is off and stay healthy everyone!
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Yeah.
Or by using a more realistic, faster and easier method:
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Using the width of your hand on your map to evaluate the fuel needed (my open hand on a 500k chart is 60Nm = 10min = 1000lbs)
or -
At “standard” drag factor (around 150) and 480kts GS:
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Below 5000ft = 20lbs/Nm
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Between5000 and 25000 = 15lbs/Nm
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Above 25000 = 10 lbs/Nm
More elaborated rough computation:
- If you are using a fuel rate value based on a clean configuration … add 30% for each 100 points of drag factor.
- If you are using a fuel rate value based on a fuel rate at sea level … subtract 10% for each 5000ft
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Yeah.
Or by using a more realistic, faster and easier method:
-
Using the width of your hand on your map to evaluate the fuel needed (my open hand on a 500k chart is 60Nm = 10min = 1000lbs)
or -
At “standard” drag factor (around 150) and 480kts GS:
-
Below 5000ft = 20lbs/Nm
-
Between5000 and 25000 = 15lbs/Nm
-
Above 25000 = 10 lbs/Nm
More elaborated rough computation:
- If you are using a fuel rate value based on a clean configuration … add 30% for each 100 points of drag factor.
- If you are using a fuel rate value based on a fuel rate at sea level … subtract 10% for each 5000ft
Now that is a “rule of thumb”- using your whole hand Thanks for sharing! I also watched your youtube video and it was a great help in actually understanding basic flying skills.
The little program is not meant to replace that.I wanted to understand the physics and math and stuff behind and learn C++. For that, it has been a success.
You won’t ever use it in-flight, but understanding the physics mattered to me- and to see if I can actually reach a specific altitude with a specific loadout in pre-planning. Or understanding how the most efficient speed is calculated by understanding induced drag and parasitic drag, playing around with the values and collecting and programming the math behind it.
It is of limited practical use (you should use rule of thumbs there), but it can be used to plan missions or check if a given speed on a given loadout can be reached or not. You can play around with the values and see what changes.
The name is probably misleading and a left-over of the initial goal, it is now more a performance calculator. I quickly realized that in order to understand all of that, I’d have to evaluate the whole model. And it was the perfect start for me in C++ since all that math stuff doesn’t actually require a UI and I was interested in everything around planes since I’ve been a little kid.
When my teacher told us to prepare a lecture in english language back in school, mine was about the different types of radars. Nobody understood a thing, even the teacher because it was complicated af, but it didn’t matter. I probably should have studied aerodynamics instead of becoming a software developer for CNC mills but my parents couldn’t afford me studying and I couldn’t join the military, so I’m left with the sim. Which isn’t that bad, since BMS absolutely rocks.
I just thought it would be a pity to not share that program for anyone interested.
It is my way to understand things (a weird one, yes, but one that works). -
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Good Job Tobias!
But indeed … on a jet, no time to use such calculator. Simple methods gives better results.
However, your calculator can be useful in some cases. -
For Dev purpose, what would be also nice to have is the fuel rate in “lbs/min” and “lbs/Nm”.
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Somewhere I read (don’t remember where, or when ) of a SOP to climb out at whatever angle of climb maintains 350kt Cal at Mil. I’ve been doing that for a long time, and it seems to work well.
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Somewhere I read (don’t remember where, or when ) of a SOP to climb out at whatever angle of climb maintains 350kt Cal at Mil. I’ve been doing that for a long time, and it seems to work well.
BMS Training Manual, p34
In this training scenario we will learn to perform a climb to altitude in a fuel efficient way. Fuel is always a
concern, so everything possible should be done to conserve fuel. One fuel efficient climb profile is to climb at
a set speed and adjust your climb angle to maintain that speed. Advance your throttle to buster (MIL power),
wait for 350 kts and then pull the stick and adjust the climb angle to maintain 350 kts throughout the climb. As
you climb, your airspeed may drop below 350 kts, in which case simply decrease your climb angle to stabilise
your airspeed and accelerate back to 350 kts. -
@jc1:
BMS Training Manual, p34
In this training scenario we will learn to perform a climb to altitude in a fuel efficient way. Fuel is always a
concern, so everything possible should be done to conserve fuel. One fuel efficient climb profile is to climb at
a set speed and adjust your climb angle to maintain that speed. Advance your throttle to buster (MIL power),
wait for 350 kts and then pull the stick and adjust the climb angle to maintain 350 kts throughout the climb. As
you climb, your airspeed may drop below 350 kts, in which case simply decrease your climb angle to stabilise
your airspeed and accelerate back to 350 kts.That’s the procedure I have been teached lately by a RL Viper pilot
Gesendet von meinem SM-G930F mit Tapatalk
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@jc1:
BMS Training Manual, p34
Thanks JC. Now I have proof I _do_RTFM.
The only question I have is,since the training mission is for a Viper, is 350 the best speed for the Hornet and Rhino ?
Update: the the Hornet NATOPS-7.2.6 Climb. For visibility over the nose, maintain 350 knots to 10,000 feet. For optimum climb
performance, refer to Part XI -
This post is deleted! -
Thanks JC. Now I have proof I _do_RTFM.
The only question I have is,since the training mission is for a Viper, is 350 the best speed for the Hornet and Rhino ?
Update: the the Hornet NATOPS-7.2.6 Climb. For visibility over the nose, maintain 350 knots to 10,000 feet. For optimum climb
performance, refer to Part XINo, it’s not. One reason is because the optimum varies with GWT - i.e.; fuel burn. The good news is that in RL the jet will calculate the speed for you - in real-time. The bad news is that this is BMS.
Oh - and the Hornet is designed so you can’t see the nose looking through the windscreen from how/where you sit - you have to really work at it to see much of the nose, no matter what you are doing.
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@DeeJay: I think I’ll update it accordingly, thanks! I’m thinking about reworking the UI because I have written a plotting application on my own which would go just nice for plotting a Vx climb or performance charts.
That will be some work though since the other application is written based on wxWidgets instead of Qt…@all: The problem with a Vx climb is that the optimum mach changes with altitude, plane, weight and your drag index. That’s why those charts are provided based on plane and drag index.
As far as I know, the math behind calculating the Vx climb is:
- Find the optimum mach by finding the lowest sum of induced and parasite drag (that’s the point on which you will have the most “excess power” available for climbing). Since induced drag largely depends on the weight and the parasite drag goes together with the drag index, both numbers are important.
- Calculate the climb angle that can be achieved taking the empty weight, fuel and weapons into account (it will be additional “drag” your are pulling up the hill)- for this, you need the maximum thrust at each altitude
- Repeat for each altitude step (1000ft or so)
As this is complicated af, the chart provides some information for the “end-user” which speed to maintain for each altitude step and drag index. It is close enough and easy enough, both at the same time. Someone else already did the math of calculating the optimum mach with an average weight, you apply the climb angle to keep that optimum mach and readjust from time to time. That’s it.
That 350kts CAS is a good number for one-size-fits all. At sea level, this equals to mach 0.53 and at FL200 it will be mach 0.76. And looking at the hornets chart, you will notice that it isn’t too far off the 125 drag index range which is similar to the viper. There is your Vx with an excellent rule-of-thumb for most loadouts, matching sea level to ~FL250. On higher altitudes, it doesn’t match that nice but that doesn’t matter. Above that height, it gets a bit complicated since the air gets so thin. -
Careful on terminology. Vx is climb angle. Vy is climb rate. Ps max is energy rate. Optimum fuel trajectory is minimum fuel from A to B. And all are different concepts.
The F-16 MIL climb schedule is a compromised optimum fuel trajectory with some weighting toward expediency. It’s similar to how airlines figure trajectories since fuel and time both cost money. The CRUS home profile is closer to an actual OFT and you notice it’s slower than MIL climb.
The F-18 climb schedule seems to weight fuel use more importantly (and perhaps not time at all) and closer to a pure OFT.
If you’re interested in minimum fuel to altitude regardless of range it’s probably an even slower/steeper than MIL or even HOME. I estimate that MFtA is close or slightly less than Vy.
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Being a Navy Operator, one of the hardest things I had to get used to was how the Viper book doesn’t pay much attention to landing GWT - on the CV your fuel state and your landing GWT are critical numbers - 1) because in general the CV is your only landing option, 2) the wire will only trap so much weight before it breaks. In BMS it seems as long as you’re not ham fisted and have enough runway you can land with any amount of GWT you take off with…not so with a Hornet.
Also, the Hornet Flight Control system design approach is distinctly different from the Viper - hence it’s operations wrt performance are distinctly different. The interesting thing to me is that most of the operational considerations for a Hornet also apply to a Viper - if you pay close attention. The biggest hang-up between the two is the Viper’s AOA limiter, but all of the notations wrt to GWT still apply if you pay attention. This is why I don’t pay strict attention to the Viper’s book in flying BMS - it’s a sim, and I want to notice and learn this stuff. I’ll live to fly another day if I crash - that’s why we have sims.
BTW - Ps is Specific Excess Power. It’s the amount of power that is available beyond that required for level flight at a given altitude for a given GWT.