Is this "unsafe"?

[SkyPiggie 0]

I have a situation upon which I would like some opinions, regarding whether or not a common practice is deemed safe.

The particulars:

A dropzone flies a Super-Otter, fully loaded with 22 jumpers aboard. It often takes off down-wind for convenience, to avoid a long taxi to the far end of the runway, saving cycle time between loads.

It does this on light-wind days, when the wind is 15 mph or less. The runway length available is 2,500 feet. There is a power line 100' off the far end of the runway, about 20' high. There is an additional 700' of runway at the near end that is unused, again to save taxi time.

In other words, the total runway length is 3,200'. The boarding area is 700' from one end, and 2,500 from the other end. Instead of taxiing from the boarding area to the far end of the runway so it can be into the wind, it just takes off from the boarding area using the 2,500' stretch, down wind. Nor does it taxi down to the closer end of the runway, for the additional 700' of length for a down wind take off.

The Otter is always airborne within 1,000' to 1,500', leaving plenty of runway to spare, and clears the far end of the runway at an altitude of 500' to 750'. The Otter is designed to do short-field take offs. It's a Super-Otter with additional horsepower engines over a standard Otter. The fuel load is kept light, re-fueling every 2nd load, with about 60 gallons. The runway is paved, and there are flat pastures beyond the end of the runway, on the other side of the power line.

Question: Do you consider a down-wind take-off in these conditions to be safe, or unsafe?

I'm intentionally omitting the name of the dropzone, as I'm not here to cast negative images at anyone. And thinking about my description, it could describe numerous dropzones that I've visited in my career. So let's just keep it generic.

I'm an active jumper at this DZ. I'm not a lawyer or whuffo trolling for negative opinions. I just want honest opinions from experienced jumpers and pilots.

[indyz 1]

I'm going to have to go with "it depends on what the POH says."

[DanG 1]

Are you sure there's a 20ft wire only 100ft from the end of the runway? That would put it at an 11.3 degree glide angle. I believe 3 degrees is the FAA standard (20 foot wire almost 400 feet away).

Maybe I'm nitpicking, but that just doesn't seem reasonable.

- Dan G

[Tuna-Salad 0]

There are too many factors to answer that as unsafe or not.
One being the outside temp. On a hot day the pilot will use up more runway to get in the air. I think that is plenty of runway to get off the ground and perform a rejected takeoff if needed.

You have to remember too.. planes burn a lot of fuel and fuel is expensive. What it costs to taxi the plane or even for it to sit and idle is a big chunk of change. So they could be trying to trim some fat off the operating cost.

I'm guessing this is a unicom field?

Millions of my potential children died on your daughters' face last night.

[EXTremeWade 0]

Although DanG makes some good points, overall, about deeming this safe or not, I feel it is safe, since there is just so much runway to deal with, even going down wind. Downwind take-offs are something I know nothing about, and I am sorry for this post, but looking at the most important factor, amount of space and time to lift off, that is plenty from the information you provide. I used to jump at a DA in AL that has a grass run-way and power lines on ends, eh...about 20 feet high I suppose but that twin otter, and caravan packed ALWAYS was airborne in less than helf the allocated runway space regardless of winds, and direction into the wind. Hope that helps. seems OK to me.

[AndyMan 7]

2500 feet of paved runway is plenty of room for an Otter with strong engines, even if you plan for an engine failure. The FAA recommends plenty of room to reach full speed, then brake to a stop. It sounds like that's well within the case.

You didn't mention the terrain off the end of the runway, and how it would support an over-run. For example, here in the midwest most runways are bounded by cornfields. Planes rolling off the end of the runway - even if they clip a powerline, likely wouldn't be fatal.

I would be more concerned if you said they were going downwind in high winds, but you said the don't do this when winds are above 15. 15 may be a bit high... I'd prefer you said 10, but I think I may be nitpicking.

__

You put the fun in "funnel" - craichead.

[nbblood 0]

I know exactly which DZ you are talking about and the situation. I have never seen a downwind takeoff that I deemed unsafe.

I have noticed the downwind takeoffs. I've also noticed that on a full load, right after refuel they will often take off into the wind, even if they have been taking off downwind prior to that.

The pilots have every bit as much interest in a safe takeoff and landing as the skydivers. I know and very much trust the VERY experienced pilot that often takes off downwind.

I also know the DZO watches the pilots closely and would be the first one screaming foul if he thought a pilot was doing something dangerous with his million dollar airplanes and the skydivers in them.

I believe that, under the discretion they use from load to load, it is safe.

Blues,
Nathan

If you wait 'til the last minute, it'll only take a minute.

[pilotdave 0]

I don't think it's black and white, safe or unsafe. There are a lot of other factors to consider, but in general it would be safer to use the entire runway and take off into the wind. But that doesn't make this unsafe. My DZ used to operate a super otter with 23 jumpers off of an 1800 foot runway. If we had 2500 feet, that would be safer. But it doesn't make operating off of an 1800 foot runway unsafe.

Now the Caravan that used about 1799 feet... that's another story.
Dave

[billvon 2,990]

>Do you consider a down-wind take-off in these conditions to be safe, or unsafe?

Depends on the load, (fuel+jumpers) condition/type of engines, temperature etc. Many dropzones do downwind takeoffs; Eloy, for example, very rarely changes takeoff direction. (They have a very long runway of course.)

[SkyPiggie 0]

Quote

Are you sure there's a 20ft wire only 100ft from the end of the runway? That would put it at an 11.3 degree glide angle. I believe 3 degrees is the FAA standard (20 foot wire almost 400 feet away).

Maybe I'm nitpicking, but that just doesn't seem reasonable.

I haven't actually measured it. There's the end of the runway, then a strip of grass, a road, and the power line on the far side of the road. Maybe it's more like 200 feet. But I don't think it's 400. The power line has those orange balls clamped on it for visibility, where it goes past the end of the runway.

[AggieDave 6]

Have you asked Rabbit about your concerns to see if he could help assuage your concerns?

On a side note, the many times I get to visit Spaceland, I've never seen them operate their aircraft unsafely.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[SkyPiggie 0]

Quote

There are too many factors to answer that as unsafe or not.
One being the outside temp. On a hot day the pilot will use up more runway to get in the air.

I'm guessing this is a unicom field?

Let's say the worst case scenario, on a 100-degree day, with 2500 feet of runway, and a full load. What wind speed would be too high for a down-wind take-off?

I'm not sure what a "unicom field" means. It's a private strip with no tower, where the pilots handle traffic control on their own over their radios. There's almost no other traffic besides the jump plane.

[SkyPiggie 0]

Quote

Have you asked Rabbit about your concerns to see if he could help assuage your concerns? On a side note, the many times I get to visit Spaceland, I've never seen them operate their aircraft unsafely.

I've added the following comment to my original post:

I'm intentionally omitting the name of the dropzone, as I'm not here to cast negative images at anyone. And thinking about my description, it could describe numerous dropzones that I've visited in my career. So let's just keep it generic.

[AggieDave 6]

Ok. I don't know who you are by your screen name, but I knew exactly where you were talking about simply by the description. If I quickly figured it out, then I'm sure that literally any other person can as well.

As a side note, the only time I've seen the runway length and winds cause an issue on that DZ was a CASA boogie that was before the runway was paved. It was very hot and the first couple of loads were flown full with jumpers. After a couple of loads and as it got hotter, the boogie pilots with the DZ limited the number of jumpers on the planes. This cost the DZ money, but it was done in the name of everyone's safety.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[wolfriverjoe 1,523]

There's an old pilot saying - "The three most useless things are Altitude above you, Runway behind you and 10 seconds ago"

Are these the most safe practices? No.

Are they unsafe? Based on the plane being off the ground in half the available runway, and clearing the obstacles with plenty of room; I can't say they are unsafe.

The DZO has a lot invested in that plane. The pilot is as intersted in safety as the rest of the people on the load. The fuel savings by not taxiing are fairly significant. I don't see it as a bad tradeoff, given the description you gave.

Edit to add: nbblood said that sometimes they do takeoff into the wind. That tells me they are evaluating the situation, and not going downwind when it isn't safe to do so.

"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

[diablopilot 2]

Quote

A dropzone flies a Super-Otter, fully loaded with 22 jumpers aboard. It often takes off down-wind for convenience, to avoid a long taxi to the far end of the runway, saving cycle time between loads.

It would save real time, and jet fuel but not "Hobbs" time, as the squat switch in the nose gear stops the Hobbs meter when the A/C is on the ground.


And I'm comfortable with the margins you've listed. While more runway is better, I feel that distances provided are sufficient.

----------------------------------------------
You're not as good as you think you are. Seriously.

[MakeItHappen 15]

Quote

I have a situation upon which I would like some opinions, regarding whether or not a common practice is deemed safe.

The particulars:

A dropzone flies a Super-Otter, fully loaded with 22 jumpers aboard. It often takes off down-wind for convenience, to avoid a long taxi to the far end of the runway, saving cycle time between loads.

It does this on light-wind days, when the wind is 15 mph or less. The runway length available is 2,500 feet. There is a power line 100' off the far end of the runway, about 20' high. There is an additional 700' of runway at the near end that is unused, again to save taxi time.
...

I know of a DZ that does this too - only they TO downwind up to 20-25 mph winds.
I have friends that won't jump there at any time or when the winds are 'higher' because of that.

The risk associated with this is that the ground speed is higher by an amount equal to the wind speed.
That means that if the AC had to abort a TO or 'crashed' after TO it would have a higher speed.
That extra energy because of the added ground speed would need to be dissipated.
I don't know what the rotation air speed of an Otter is, but the calculation to figure percentage increase in kinetic energy is a simple high school physics problem. The speed that is important here is the ground speed.

Whether it is 'safe' or not is a personal or societal acceptance of a given risk.
FMI see
About Risks
Risk and Safety

From a liability standpoint, a DZO/pilot would have a hard time justifying taking off downwind when the winds are high, especially if something bad happened.

A pretty graph is attached.

Example Comparison:
Suppose rotation air speed was 100 kts and wind speed was 10 kts.
The difference in KE between a downwind TO and an upwind TO would be about 40%.
That is significant in an aborted TO or crash shortly after TO.

.

.
Make It Happen
Parachute History
DiveMaker

[wmw999 2,442]

This might be a better question to ask pilots than skydivers.

I believe this same DZ quit filling its Caravan because it was concerned about how close it came to the power lines after the first couple of full takeoffs. And they keep the runway extension in good shape so that it's quite usable. Yes, they do take off downwind in low winds.

No DZ is perfect, is it. But the best way to address that is probably to talk to the pilot and ask him what his thoughts are -- is this something the DZO wants to do, or is it something the pilot suggested based on his experience?

Wendy W.

There is nothing more dangerous than breaking a basic safety rule and getting away with it. It removes fear of the consequences and builds false confidence. (tbrown)

[AndyMan 7]

Quote

I also know the DZO watches the pilots closely and would be the first one screaming foul if he thought a pilot was doing something dangerous with his million dollar airplanes and the skydivers in them.

As an aside, I dislike the notion that we ought to trust our DZO's simply because their planes are expensive, or because the planes are full of skydivers.

History has shows DZO's willing to risk both in the sake of profit.

The trust of our DZO's is not given. It is earned by continually observing safe practices. Whether this situation fits is an exercise for the reader.

_An

__

You put the fun in "funnel" - craichead.

[nbblood 0]

Agreed. In this case, the DZO's trust has been earned. If you were at the DZ and saw the oversight on a meticulous maintenance program, $$ spent on expansion for the benefit of safety and comfort at the risk of loss of profit, and general oversight of all operations, I think you would agree.

Trust is earned. DZOs should be judged on a case-by-case basis. In this case it most certainly is earned, IMHO.

At the same time, skydivers are often judgmental of a DZO that is trying to make a profit. It is a business and in some cases the DZO's only livelihood. As it is in this case. I think there are a lot of "sour grapes" cases pointing fingers at DZOs because they're trying to be successful businessman. That is just as much BS as the other way around, IMHO.

Blues,
Nathan

If you wait 'til the last minute, it'll only take a minute.

[SkyPiggie 0]

Quote

This might be a better question to ask pilots than skydivers.
I believe this same DZ quit filling its Caravan because it was concerned about how close it came to the power lines after the first couple of full takeoffs. And they keep the runway extension in good shape so that it's quite usable. Yes, they do take off downwind in low winds...

Actually, the DZ I was thinking of doesn't operate a Caravan. So, once again, I'm not picking on any particular DZ. But your interpretation of circumstances just goes to show that the scenario described can fit at many different drop zones. So this issue is not about any one place in particular, but about a general practice at many places. Therefore, we shouldn't be singling out here any one place as the target for negative inferences. I don't want this to be an attack piece on one drop zone. I want it to be a generalized discussion about the pros and cons of this kind of procedure.

[riggerrob 643]

It all depends.
How much is he missing the wires by?

[nbblood 0]

Quote

It all depends.
How much is he missing the wires by?

From the OP

Quote

The Otter is always airborne within 1,000' to 1,500', leaving plenty of runway to spare, and clears the far end of the runway at an altitude of 500' to 750'

Blues,
Nathan

If you wait 'til the last minute, it'll only take a minute.

[squarecanopy 0]

SkyPiggie,
The individual pilot is a large factor here. Years before I started jumping I accumulated a few thousand hours in GA aircraft, from Luscombes to King Airs, even had rides in Lear Jets and Sabreliners. I have flown with pilots who should not ever take off downwind on a 7000 ft strip in a small STOL aircraft, and pilots who could shoehorn a fully loaded Cessna 180 in and out of an 800 ft runway on the side of a mountain. I think that with an experienced pilot who knows his limitations and those of the airplane, along with a fair amount of experience with that particular airport, what you are describing is safe.

Just burning a hole in the sky.....

[erdnarob 1]

What creates the lift on a wing is its shape and the speed of the relative airflow with respect to the wing.

Example: Let suppose an airplane needs 70 MPH of relative airflow to take off (lift higher than the weigth) and there is a wind of 20 MPH. In these conditions:

1) taking off upwind (nose wind) means that the airplane needs to have a ground speed 70 - 20 = 50 MPH for take off since at rest there is already a relative airflow of 20 MPH. Therefore the takeoff distance will be shortened and if there is a engine problem there is a maximum of clear space ahead to stop.

2) taking off downwind (tail wind) means that the airplane needs this time to reach a ground speed of 70 + 20 = 90 MPH since at ground speed of 20 MPH the airplane is going at the same speed and same direction than the wind and will have zero relative air flow with respect to the wing. The airplane will need an extra 70 MPH to buit up the take off speed going now at 90 MPH then almost doubling the distance needed.

3) if there is no wind at all, any direction for take off is OK provided the length of the runway is OK

Taking off downwind is OK only when the length of the runway is quite important. But a wise pilot should be very cautious for doing so.

Learn from others mistakes, you will never live long enough to make them all.