Mid-runway departure?

Would you request or take a departure from B2 in a 172?

  • Yes. Depart from B2 on R14

    Votes: 50 72.5%

  • No. I'd taxi all the way to the end and takeoff.

    Votes: 19 27.5%
  • Total voters
    69
  • Poll closed .
M

mikegreen

Pre-takeoff checklist
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mike g.
Not sure intersection departure is right.. but maybe similar thinking.

For KJVL, runway 14 is 7301' long.
Assume you're in a 172 at the jet center, which is all the way at the end of 14, and departing 14.
http://www.aopa.org/airports/KJVL


Would you ask for a takeoff at B1 or B2 to save taxing over a mile down? Consider you need 1500 for takeoff?

*edit*
added a poll.. and here is the airport diagram
2011-04-28_1408.png


just wonderin'

regards,

Mike
 
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Would I decide to start my departure by leaving half the runway behind me? No. Not generally. I've done it exactly once in 450+ hours of flying. That said, lots of folks do it.
 
I won't ask for one under any circumstances that I can currently conceive of.
When offered one, my response is "how much useable runway will I have?". Less than 4000' and I will probably say "no.".
(I also only need about 1500' for a normal takeoff.) Runway behind you is as useless as fuel in the truck.
 
I'll ask for intersection departure. IMO half of 7301' is enough for C172.
 
Seems to be LOW risk. Many pilots accept LAHSO, but again its pilots discretion.
 
As a single point of reference, I used to fly from a 1900' runway, and one frequent destination was Keene, NH. http://www.airnav.com/airport/KEEN

When departing (preferred runway is 2, restaurant is at other end), I would taxi to the A intersection and depart from there. I didn't bother back-taxiing from that point. Departing from the C intersection would have given me over 3000', but I opted for the 4500' to 5000' option.

Like I wrote, most of my operations were from a 2000' runway.
 
I've departed SAW at an intersection and still had over 6500' of runway in front of me. I also had almost that much behind me too.
 
I do it all the time, so yes. But then, I'm based at a 2500' runway and fly often to shorter. For those that said they'd never consider leaving runway behind them, do you ever fly out of short runways where DA and performance matters?
 
The Old Man said:
I won't ask for one under any circumstances that I can currently conceive of.
When offered one, my response is "how much useable runway will I have?". Less than 4000' and I will probably say "no.".
(I also only need about 1500' for a normal takeoff.) Runway behind you is as useless as fuel in the truck.
Click to expand...
Most of the places I see that will permit intersection takeoffs give you at least 4000 usable from the intersection.
 
Re: Mid-runway departure? how about run-up area departure?

I would consider a lot more than the runway left. If I had a 20kt headwind my ground speed and distance to stall speed are severely reduced. My ground distance on climb out are reduced as well.

Are there trees buildings? is there an alternative landing site like a field ahead or alongside or is it housing and industrial?

I took off one time at the old airport in Rio Vista Ca. The wind was picking up as I arrived in the run up area. During run up with the brakes locked ans set I lifted off. That is a ZERO runway distance! Got on the radio and warned that I had taken off from the run up!:hairraise:

Another question might be how one feels about a quick wing over or other emergency procedure and at what altitude your aircraft can perform that kind of maneuver.

There is much more to consider than how much runway one has.
 
Now that I have my C172 POH handy I will back up my answer with the numbers:
Assuming weight 2300 elevation 1000' lift off 52 at 50' 59
Temp GND ROLL CLR 50' OBS
10C 850 1525
20C 915 1630
30C 980 1745

I'll have ~2000' runway in front of me after clearing 50'. Pretty good safety buffer.
 
Can I safely take off in the distance given not using short field technique? If the answer is yes, I will accept the intersection departure. I have asked for it in more than one instance to save time. The real question is whether or not I'll need to use short field technique for a safe departure. The one exception would be if I'm on a maintenance flight after a repair. The reason for the short field technique being the decision factor is just personal preference, nothing more. I have no problems using short field technique on short fields.

Then again, like our Pitts-flying friend, I fly out of short strips routinely. I even fly out of short strips with obstacles that sometimes have ice on the runway or are otherwise not paved.
 
PittsDriver said:
I do it all the time, so yes. But then, I'm based at a 2500' runway and fly often to shorter. For those that said they'd never consider leaving runway behind them, do you ever fly out of short runways where DA and performance matters?
Click to expand...

I've flown into many places where DA and performance mattered. The real question is why start with runway behind you? Is that five minutes you saved really worth it if you have a problem on climb-out? My vote is no, the five minutes isn't worth it. Other folks make other choices. I had an instructor tell me to make an intersection departure out of Salina KS (loooooonnnnnnggggg runway) at night. I didn't do it.
 
Living at high DA, I've simply become accustomed to using all available runway.
That said, I don't know that I would take B2, I would almost certainly take B1.

Some will say there's plenty of runway, and yes, I would fly into a 1500 or 2000' strip at sea level.
But I'm conservative at heart and there's multiple times in my EMS, law enforcement, and hazmat career where that trait has saved my life.
Yes, you'll almost certainly not need the extra runway, but you only have to need it once to change your operating assumptions.
 
Generally I say no to intersection departures.

It comes down to wondering how I would answer the question: "Why did you elect not to utilize the full runway length?" in front of an FAA Attorney or Administrative Law Judge.

Rarely have I felt I was in a situation where I would have an adequate answer as to why my decision to use less runway would have made the flight safer.

Expedient, yes. Safer, no.

I've done it at *huge* airports where there was no possible way another couple of thousand feet would give me any additional safety margin. Even then looking back on those times that I can count on less than one hand, I see hints of "schedule-itis" pushing me to get launched.
 
Whether or not the extra runway will help you depends on the circumstances.

Let's say you take off on the 7300 ft runway using full length. You get up to 500 AGL 2/3 down the runway when your engine quits (I don't know if that number is accurate or not, just guessing). You have runway left, so you decide to make it. Then you run off the runway at the obstacles, instead of landing in the adjacent field that would have been the automatic response if you'd taken off from a 2500 ft runway and were at 300 AGL.

Obviously that scenario may not ever exist, but the extra runway can only help you in certain cases, V1 cuts being the primary ones. In some cases, having too much runway may induce a bad decision if you try to land when you don't have enough remaining. Regardless of what you're flying, you should have your decisions made on what to do in the event of an engine failure at every point along your critical phases of flight (or in general, but in cruise you do have more time to work with).

The fuel you left in the truck is much more useful if taking off with too much fuel causes you to have poor takeoff performance causing you to run off the end of the runway (which you didn't leave any runway behind), and the altitude is useless if those extra headwinds you got up there caused you to run out of fuel (that you didn't leave in the truck). I don't like that "three most useless things" phrase because, as with the rest of aviation, it depends.
 
The Old Man said:
I won't ask for one under any circumstances that I can currently conceive of.
When offered one, my response is "how much useable runway will I have?". Less than 4000' and I will probably say "no.".
(I also only need about 1500' for a normal takeoff.) Runway behind you is as useless as fuel in the truck.
Click to expand...

Is 4000' your minimum length? Do you decline to use any airport with less than 4000' of usable runway length available?
 
Clark1961 said:
I've flown into many places where DA and performance mattered. The real question is why start with runway behind you? Is that five minutes you saved really worth it if you have a problem on climb-out? My vote is no, the five minutes isn't worth it. Other folks make other choices. I had an instructor tell me to make an intersection departure out of Salina KS (loooooonnnnnnggggg runway) at night. I didn't do it.
Click to expand...

How much time needs to be saved to be worth it? Let's say there's an air carrier at the end of the runway that drew a twenty minute departure delay. Your choice is to take an intersection departure with 4000' of runway available or wait behind the air carrier for the full 7300'. Do you wait or depart from the intersection?
 
denverpilot said:
Generally I say no to intersection departures.

It comes down to wondering how I would answer the question: "Why did you elect not to utilize the full runway length?" in front of an FAA Attorney or Administrative Law Judge.
Click to expand...

What event brought you in front this FAA Attorney or Administrative Law Judge?
 
Clark1961 said:
Land and hold short is very different from an intersection departure.
Click to expand...
It may be different, but I believe his point was that in accepting a LAHSO, the PIC is giving up useable runway which is what you are also doing by accepting an intersection departure.
 
PittsDriver said:
I do it all the time, so yes. But then, I'm based at a 2500' runway and fly often to shorter. For those that said they'd never consider leaving runway behind them, do you ever fly out of short runways where DA and performance matters?
Click to expand...

I am based out of, and learned to fly at a 2975' X 40' strip. I have done many, many, many T&Gs at that strip. Most recently last month.

The point remains that runway behind you is worthless. An aborted takeoff from near flying speed eats up nearly all of that 3000' (I've done it twice in 10 years). If it is available, I prefer enough concrete to abort without standing on the brakes.

To me, abort distance is probably more important than re-land distance.

I've been to <3000' strips and have no problem with that. I do have a problem with leaving runway unused runway behind when it only costs a minute to taxi another 1000'.
 
denverpilot said:
Generally I say no to intersection departures.

It comes down to wondering how I would answer the question: "Why did you elect not to utilize the full runway length?" in front of an FAA Attorney or Administrative Law Judge.

Rarely have I felt I was in a situation where I would have an adequate answer as to why my decision to use less runway would have made the flight safer.

Expedient, yes. Safer, no.

I've done it at *huge* airports where there was no possible way another couple of thousand feet would give me any additional safety margin. Even then looking back on those times that I can count on less than one hand, I see hints of "schedule-itis" pushing me to get launched.
Click to expand...
Try flying an Aeronca Champ at SDM and using full length (8000')....oh and the tiedown for the Champ is at the opposite end of that 8000' runway.

There is nothing to be gained by using full length. If you takeoff at C, you are at pattern altitude long before you've gone past the end of the departure end of the runway.
 
I dunno...B2 looks to be about 500'. Might be a bit short for the Chief, but into a good headwind, maybe.. ;-)
 
It all depends on the airport, the traffic, and local procedures.

Some airports (KNEW for one, KCLT for another) used to (and may still) ask small GA to take an intersection takeoff if possible. Assuming there's no risk of wake turbulance & sufficient length for my operation, I'll accept. Other airports want you to use whole length as part of local procedure, and I have no issue with that at all, especially if I can get an early turn and be on my way....
 
Another factor to consider is what is at the end of the runway?

The available runway may be more than enough to safely takeoff, but if there is alot of development near the departure end of the runway, I'd be alot less inclined to attempt an intersection departure. I generally don't like to be 200-300 feet above houses or other buildings when I'm climbing out.

In the JVL example given, it looks like mostly flat undeveloped land beyond the departure end of 14. I'd be comfortable doing an intersection departure there if they offered it.
 
In this case, I'd take the intersection. Here's why:

1) There's still enough runway left if you lose an engine early in the climbout to land on the remaining runway.

2) With the three runways in that configuration, the "impossible turn" is much more possible - For example, by taking a left and landing on 36 you only have to make about 1/2 the turn that you'd need to return to the same runway. So, I would say that by the time you're high enough that landing back on 14 isn't an option, you're in a position to land on 36 instead.

3) There's nothing off the end of 14 at KJVL IIRC - The airport is south of town and 14 would be going away from town. So, no worries about being low over a populated area after departure.

I really don't think there is a downside to the intersection departure *IN THIS SPECIFIC CASE*. (Like Ron says, "It's all situations.")

Also, how many times have we derided people who won't land a 172 on less than 3000 paved, and here we are saying that taking off with more than that is foolish? If this was a 7300-foot runway surrounded by trees, mountains, etc. and I was flying something that needed lots of runway it'd be different - But it's not.
 
wsuffa said:
It all depends on the airport, the traffic, and local procedures.

Some airports (KNEW for one, KCLT for another) used to (and may still) ask small GA to take an intersection takeoff if possible. Assuming there's no risk of wake turbulance & sufficient length for my operation, I'll accept. Other airports want you to use whole length as part of local procedure, and I have no issue with that at all, especially if I can get an early turn and be on my way....
Click to expand...

Most places I've been to lately don't ask, and if you ask, they make sure to say it's an intersection departure per the controller's regs. It goes on the tape.

Someone asked me what I would have done that would garner attention from the FAA... That's easy. [Insert ANY accident here.]. The lawyers WILL add an intersection takeoff to the list of questions just to find out if it "lowered safety" in any way. Even if the accident was an Armadillo walking out in front of you. And if not the FAA, the insurance company lawyers will.

Not saying I wouldn't accept an intersection takeoff or ask for one. Just saying I need a reason other than not wanting to taxi another couple of thousand feet.
 
denverpilot said:
It comes down to wondering how I would answer the question: "Why did you elect not to utilize the full runway length?" in front of an FAA Attorney or Administrative Law Judge.
Click to expand...

My answer would be that I did so because I had about a 500% margin from that intersection and runway length wasn't a factor in why I'm standing here.

*shrug* there's no right answer to this question and whatever makes people sleep good is a fine answer. Heck, I'd take B1 going the other way with no obstructions. It looks like it's more than 8-900' from there.
 
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PittsDriver said:
*shrug* there's no right answer to this question and whatever makes people sleep good is a fine answer. Heck, I'd take B1 going the other way with no obstructions. It looks like it's more than 8-900' from there.
Click to expand...

Precisely right. The question is what would *I* do, not what I think everyone else should do. Each of us is PIC and makes (and is responsible for) our own decisions.
That's one of the things I love about flying,
 
172 with <2500' in front of me at less than 1000' of altitude... There would need to be extenuating circumstances for me to go to full length for that, otherwise, I'd leave from midfield there...
 
Here's another airport diagram. I have departed 35R from A16 (or whatever it was called in those days) more times than I could count in a Cessna 206. I also departed many times, by choice, on 10 when going east. For those who would not choose A16 would you choose 10? How about if there was a long line of airplanes at the end of 35R or 17L and the tower said you could get out quicker that way. If 35R was closed, would you use 35L? I know it depends on the airplane but I'm just curious about what people think.

05715AD.PDF
 
The link isn't working in Tapatalk but that sounds mysteriously like my home 'drome of KAPA... ;)
 
Here's one for you, KTPA.

I was there last fall in a 172. I was parked near the intersection of R and E (bottom right). Winds were 090@12. I was instructed to taxi for a 19L departure, with several large jets in front of me (for a crosswind takeoff). I requested a departure from runway 10 at E, and tower cleared me for that. Runway 10 wasn't in use at the time, but it was right into the wind and the approx 4,000' remaining were much more appealing than taxiing behind 737s that might have to hold for release, have a 12kt crosswind, wake turbulence, and a longer route for my eastbound departure. That one was a no brainer for me.

(Actual runways back then were 18L and R, and 09, but were renumbered recently)


1
 
It's a question of how much risk you're willing to accept, and that will depend on a huge number of factors. If I've got paying pax or my family on board, I try to reduce risk whenever possible, and would take the full runway. If it's just me or myself and another CFI, or even with a student, I'm likely to take the intersection departure, because it's no riskier than our "normal" operations at home base. If there's a delay or something else at the ful length to make it less attractive, that matters too.

Heck, if I wanted minimum risk, I'd have stayed home!
 
No. Consider the accident report. "Pilot departed 23 at N, with 4000 feet available. Lost power, Leftt engine, attempted to abort, overran and suffered major damage and fire".

Now read the report with 6300 extra feet:

"Pilot lost Left engine on departure, landed straight ahead, but had to be towed off to pad 5".

When V1 is less than Vyse, I'm aborting in a light twin, and for a Seneca II, even lightly loaded on a hot day, that's 4,700 feet. No freaking way. Think, "what would the accident report look like?" every time. I'm taking 11,000 feet.
 
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