Poll; Ground roll timing

[FastEddieB]

But it changes by temperature and load, so there is no one number.

And altitude and runway surface. So the premise of the whole thread is rather pointless.

Edited to add: I see Clip4 already touched upon this.

 

[Dave Theisen]

<snaps fingers> dang, I've been doing it all wrong. I should have been watching the clock instead of the ASI?

I'll do the one Mississippi thing too just for S&Gs.

I wasn’t convinced that you were looking at the ASI either.

 

[ateamer]

So about a 450' ground roll then?

That sounds about right. I’ll drop a mental place marker at the liftoff point tomorrow and pace it off to confirm.

 

[EdFred]

And altitude and runway surface. So the premise of the whole thread is rather pointless.

Edited to add: I see Clip4 already touched upon this.

obviously you didnt see Dave's follow up post regarding takeoff run time vs base to touchdown time. So not pointless at all. The airport isnt all about you and your plane.

 

[Let'sgoflying!]

obviously you didnt see Dave's follow up post regarding takeoff run time vs base to touchdown time. So not pointless at all. The airport isnt all about you and your plane.

Many skimmed the thread and assumed it was about aircraft performance; no biggie.
I timed mine today, near max gross and 27C was about 25 seconds.
So someone just turning base should not feel like they own the runway yet.
My decision to take off in no way caused the other pilot danger. If he firewalled it, he could not have hit me. It's just a perception or maybe an attitude problem. Also no biggie.

 

[woodchucker]

A plane turning base (if they call it accurately) will not be a factor for a plane holding short ready to roll.

That is NOT getting cut off. Just tonight did the exact same thing with a sport cruiser calling a turn to base. I’m not waiting for that. A plane established on base? Yeah, I’ll wait.

 

[NealRomeoGolf]

I should time the A380 I am flying (as a passenger) on Saturday.

 

[EdFred]

A plane turning base (if they call it accurately) will not be a factor for a plane holding short ready to roll.

That is NOT getting cut off. Just tonight did the exact same thing with a sport cruiser calling a turn to base. I’m not waiting for that. A plane established on base? Yeah, I’ll wait.

Depends on the plane, and where he is on base, and what I'm flying. A 172 established on a half mile base or more: I'm rolling if I'm in anything that faster than a 172.

 

[danhagan]

A plane turning base (if they call it accurately) will not be a factor for a plane holding short ready to roll.

That is NOT getting cut off. Just tonight did the exact same thing with a sport cruiser calling a turn to base. I’m not waiting for that. A plane established on base? Yeah, I’ll wait.

Yep ...

Depends on the plane, and where he is on base, and what I'm flying. A 172 established on a half mile base or more: I'm rolling if I'm in anything that faster than a 172.

Normal pattern, should be no factor as long as they haven't turned final , but you can't Lolly-gag.

 

[flyingron]

I guessed 11 seconds, but it's probably less depending on the winds and the runway surface. It doesn't take that long for the Navion to get to rotation speed (60 MPH). It only takes a fraction of a second after applying the backpressure to leave the ground. The Navion is spec'd for a calm wind 850' ground roll, even at a smooth, even acceleration from 0 .. 60 over that distance, it's 18 seconds.

Ground roll TIMING isn't a big thing. DISTANCE is. I plan a go/nogo point where if I'm not flying, I'm going to abort.

 

[NealRomeoGolf]

I timed both an A380 and an A330 yesterday. Interestingly they were both 58 seconds. The temps were different. The A380 was at about 14C and the A330 was 31C. So there’s that.

 

[Sac Arrow]

Can you allow multiple votes?

 

[Let'sgoflying!]

Can you allow multiple votes?

yes

 

[Southpaw]

My CFI has me fly in ground affect till end of runway. 5500 ' runway . The neighboring hanger has a citation sovereign, its off in less distance than I taxi .

 

[flyingcheesehead]

My CFI has me fly in ground affect till end of runway. 5500 ' runway.

Why?

 

[Southpaw]

Good question, will ask him next time out.

 

[Kenny Phillips]

The time is irrelevant! The thing that counts is distance! You should know how much runway is needed and do something is the airplane is taking to much distance.

Yep, same for me.

 

[Let'sgoflying!]

So if you are looking at 'if there will be a conflict between you and a guy turning base' (as described in this thread) then you want to know how many feet down the runway you will lift off.
I asked about timing because that's the only way I could figure out the possibility of a conflict.
Will look at the distance to lift-off suggestion too.

 

[dbahn]

So if you are looking at 'if there will be a conflict between you and a guy turning base' (as described in this thread) then you want to know how many feet down the runway you will lift off.
I asked about timing because that's the only way I could figure out the possibility of a conflict.
Will look at the distance to lift-off suggestion too.

Actually, if you want to know what will be a "conflict" you'll need to know the risk tolerance of the pilot on base. Some pilots will freak out instead of just continuing the approach, and in that case aborting the landing may be the riskier action than just landing close behind the departing aircraft, especially if he starts slowing the approach, doing a 360, etc.

 

[Let'sgoflying!]

Actually, if you want to know what will be a "conflict" you'll need to know the risk tolerance of the pilot on base. Some pilots will freak out instead of just continuing the approach, and in that case aborting the landing may be the riskier action than just landing close behind the departing aircraft, especially if he starts slowing the approach, doing a 360, etc.

yes, and I was hoping to get some numbers ie, the average C150 turning base using typical speeds, no wind; my turning onto the runway & powering up then 25 seconds to liftoff - how much time will he get between my departure and his touchdown. I have a good idea of that now.
I am fortunate to mostly fly out of places where the controllers will time things well - or at non-towered airports, we all are eager to be helpful to each other and in this case, would extend downwind a few seconds to accommodate a departure.

 

[dbahn]

yes, and I was hoping to get some numbers ie, the average C150 turning base using typical speeds, no wind; my turning onto the runway & powering up then 25 seconds to liftoff - how much time will he get between my departure and his touchdown. I have a good idea of that now.
I am fortunate to mostly fly out of places where the controllers will time things well - or at non-towered airports, we all are eager to be helpful to each other and in this case, would extend downwind a few seconds to accommodate a departure.

I'd be careful about doing too much math to manage this decision, any more than you would use a stopwatch to decide that you can pull out in front of another car. If there's any doubt, it's safer to wait. If it looks as if there is plenty of space, then you pull out. Even the decision to pull out in a car will take into account the apparent speed and distance of the other car without a time calculation.

As I mentioned earlier its distance and speed, not time that counts. And it's primarily done without any attempt at a precise calculation, which would need an accurate measurement (not an estimate) of distances as well as speeds, neither of which you have for any given situation. Besides, would you really make that decision based on knowing that your ground roll is going to be "x" seconds? Again, if I'm taking off in a Cub and you're landing in a Malibu I'm still going to interfere with a safe landing if I use that calculation to enter the runway.

 

[flyingron]

I used to watch (and flew on a few times) the transpacific flights departing out of IAD. They used up every inch of the 11,000+ runway and still just barely lumber into the sky (and have to refuse even the slightest tailwind on takeoff).