Take off ground roll
Posted by Most_Implement6306@reddit | flying | View on Reddit | 17 comments
Hello,
When I was calculating a take off ground roll with a graph chart, I had a question in my mind. It won’t be a matter if I have a enough runway distance, but what if I have some kind of fit runway distance like, my take off ground roll is 1,500’ and planned runway distance is 1,550’. How do you guys determine if a runway distance is enough or not? Is there a specific recommend regulation in FAR like plus or minus 300’ or 500’ something like that?
Bravo-Buster@reddit
I like being able to have tires off the ground at or before 1/2 the runway length. If they're not, I know I have a problem and need to shut it down. That's very conservative, but I'm doing this for fun and transportation. I don't need to tempt fate.
iamflyipilot@reddit
Do you always follow this rule regardless of runway length?
Bravo-Buster@reddit
I fly out of a 6,000' runway, so yeah, if I'm at halfway in the Archer and those wheels haven't came up yet, I have problems!
I don't usually fly into less than 3,000', just based on the places I travel to, so it still works.
Book value is 1,135' roll; if it takes another 50% of that on a 3,000' runway, basically the same thing, I know I have a problem (or it's just hot as hell in Houston, but I'll know that beforehand if I need to actually do math first).
Most_Implement6306@reddit (OP)
Many people replied for me. I may add rule of thumb 25%-50% to the result of calculation because there’s no offical regulation. Thank you all.
iamflyipilot@reddit
It is also very important to calculate your actual expected take off point per the book. This can help aid it identifying a potential problem on the take off roll.
rFlyingTower@reddit
This is a copy of the original post body for posterity:
Hello,
When I was calculating a take off ground roll with a graph chart, I had a question in my mind. It won’t be a matter if I have a enough runway distance, but what if I have some kind of fit runway distance like, my take off ground roll is 1,500’ and planned runway distance is 1,550’. How do you guys determine if a runway distance is enough or not? Is there a specific recommended regulation in FAR like plus or minus 300’ or 500’ something like that?
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Mizzle6@reddit
The book says takeoff ground roll is 1,500. You have 1,550 feet available. Is it legal? Yes. Is it SAFE? Depends on experience, judgement, and common sense.
Did you account for all factors in the notes of the chart? Are you going to do a full power application with the brakes locked before releasing? Runway slope? Are you below the maximum takeoff weight of the aircraft? Is the engine and prop in great condition? If you don’t know how these factors will affect the number you calculated you need to proceed with caution.
Conservative estimate is use the takeoff distance over a 50’ obstacle as a ground roll. You can even add 10%. Real world: if I needed to clear an obstacle I’d calculate the distance using the 50’ obstacle chart and add a MINIMUM 25% to that figure.
Good-Cardiologist121@reddit
I don't like the idea of seeing if I'm good enough to match the test pilot when performance is that critical.
CorporalCrash@reddit
Lots of aircraft have charts to calculate takeoff distance over a 50 foot obstacle. So if your available takeoff distance is less than that and you have obstacles near the end of the runway you run the risk of hitting something
Jwylde2@reddit
You may want to consider takeoff roll distance + distance allowance for engine loss during takeoff
redditburner_5000@reddit
My rule of thumb is that I want a runway that is as long as the 50' obs clearance distance.
Performance charts are all make believe.
Plastic_Brick_1060@reddit
Don't forget about obstacle and terrain clearance when you're considering a runway
Solid-Cake7495@reddit
If you're.operating privately, it's all down to the size of your cajones. Under commercial, regulatory factors come into play.
CluelessPilot1971@reddit
Small planes under Part 135 also have very minimal regulations.
N546RV@reddit
Basically a judgment call. Keep in mind that the book figure is a best-case scenario, assuming a healthy engine putting out rated power, a pilot who is right on the money with the short field procedure, and accurate conditions used for the calculation.
Consider that any one of those things could result in you not making the book performance. Maybe that engine is tired and down by ten horsepower. Maybe that 10-knot headwind died down while you were on the way to the airport.
A good way to think of any aspect of flight planning, whether it's takeoff/landing performance, expected fuel burn on a cross-country, or anything else, is "how wrong would my calculations have to be for me to have a bad day?"
If your calculated takeoff roll is 1500' and the runway is 1550', then the answer to that question is "not very wrong at all." So then the question becomes how confident you are in your calculations. If you assumed zero headwind regardless of what the forecast said, then that's one concern checked off the list...but what about the rest?
My baseline opinion would be book numbers + 50% for a good healthy safety margin.
Unlucky-You-6260@reddit
Is a personal preference, better to have an extra 500 to be short 500
JonathanO96@reddit
No regulation, just personal preference for that. Some people say POH is enough, some people add 50%, some people double it. It’s a personal minimum question ultimately.