DPV training books

[PfcAJ]

What you're talking about here are what most people call safeties, not stages. A stage is typically thought of as a cylinder you count in your gas plan and breathe from during the dive. A safety is a cylinder you place in the system because you're planning a big dive and want the added "safety" in case something goes wrong. But you still don't count that in the gas plan. It's just there as an added buffer.

Even with a backup scooter I still plan on having enough gas to swim out and decompress with a scooter failure. I borrowed a scooter for backup once and when I got back to the cavern I was going to take it for a quick spin. When I hit the trigger all the props flew off. Someone had put them back on incorrectly. Fortunately I didn't need that scooter during the dive. This wouldn't likely happen to me if it was my own scooter but, unfortunately, I only have one scooter (the Makos don't count) so any backup scooter right now would have to be borrowed.

Oh, and for solo scooter dives you have to gas plan very conservatively. I've done quite a few solo scooter/swim dives in the 3000-4000' penetration range and I always come out with tons of gas left.

Why would you not test it before the dive? Gotta test each scooter before the dive starts. My pre-dive routine involves pitching, running, and de-pitching each scooter.

Scooters are extremely suspect, even the fancy/expensive Italian jobs.

[a64pilot]

RN, yeah I guess I'm thinking safeties, not stages, but you get the idea, the thought was have a bunch of extra un-needed gas available just in case, but don't have it in the plan.

PfcAJ, trust me, if it's man made it will fail at the most inopportune time, I don't care how often it's tested or how well it's maintained, it will fail.
I'm an old helicopter pilot, and I almost relax in an emergency, it's not the emergency that bothers me as much as waiting for it's eventuality, I know it's going to happen, but I hate watching and waiting for it.

"The thing is, helicopters are different from airplanes. An airplane by its nature wants to fly, and if not interfered with too strongly by unusual events or by a deliberate incompetent pilot, it will fly. A helicopter does not want to fly. It is maintained in the air by a variety of forces and controls working in opposition to each other, and if there is any disturbance in this delicate balance the helicopter stops flying, immediately and disastrously.
"There is no such thing as gliding helicopter!"

"This is why being a helicopter pilot is so different from being an airplane pilot, and why, in general, airplane pilots are open, clear-eyed, buoyant extroverts, and helicopter pilots are brooders, introspective anticipators of trouble. They know if something bad has not happened, it is about to."

- Harry Reasoner
July 1977

[jj1987]

PfcAJ, trust me, if it's man made it will fail at the most inopportune time, I don't care how often it's tested or how well it's maintained, it will fail.

I think PFCAJ was just stating that a "walk around" would have caught this before the dive-- it would have been a quick fix and the safety scooter would have been used.

Talk to people who have experienced catastrophic scooter failures-- nearly every one (not all, but darn close) is centered around the scooter not put together correctly after working on it, not burn testing (or not charged), going below it's depth rating or getting line caught in the prop. All but the line issue can be solved at the surface, before the dive.

[a64pilot]

I think PFCAJ was just stating that a "walk around" would have caught this before the dive-- it would have been a quick fix and the safety scooter would have been used.

Talk to people who have experienced catastrophic scooter failures-- nearly every one (not all, but darn close) is centered around the scooter not put together correctly after working on it, not burn testing (or not charged), going below it's depth rating or getting line caught in the prop. All but the line issue can be solved at the surface, before the dive.

Your right, I inspect and test. That catches quite a lot of things before they become failures, just I have the mindset that everything will fail, just give it time. My scooter failure for example was a bad cell in the battery, completely undetectable until that one cells voltage fell below the cut off point in the battery management module and it interrupted power, so it went form a perfectly functioning scoot, to a dead one with no warning. I'm actually surprised that I haven't had more things fail on me more often than they do. I'm real new to this scooter thing, and yet have already had it fail once Murphy and I are well acquainted with each other.

[DA Aquamaster]

I think Mr. Reasoner's statement has to be taken in the context in which it was intended. Helicopters still autorotate pretty well (short of a catastrophic transmission failure or losing a rotor) and they'll usually fare far better than a fixed wing aircraft after engine failure, especially when making a forced landing in rough terrain. In fact, at one point the Bell 206 was even ranked as the safest GA aircraft based on accident statistics and it's pretty much always near the top.

Of course that does not change the fact that they are an abomination and only fly because the earth rejects them.

----

I am a big believer in pre-flights, but you also have to be careful/reasonable with your procedure.

For example the Oceanic prop hub is very common on many scooters and uses a plastic yoke to maintain prop pitch via a pin on the blade shank. As long as you have free and complete movement of the hub and blades, it will de-pitch if the scooter won't turn off. Testing it before each and every dive by actually tapping the hub with the prop moving is pointless and just adds needless wear and tear to what is already the weak point in the entire design. And if it fails, the prop will go into fine pitch and leave you with a useless scooter.

Consequently, I check for free and complete movement of the hub and blades, but I'd don't test the de-pitch feature.

----

I am not a big believer in burn testing as it tells you very little about trends and is itself pretty hard on the battery. It's also pretty meaningless unless you actually know how many amps our motor pulls under various conditions. I do use a data logger to monitor battery performance during the dive and I also use it during the charge. So far I've gotten ample warning of a battery that is starting to go south as it's performance starts to sag before a cell fails completely.

[gschaut]

"The thing is, helicopters are different from airplanes. An airplane by its nature wants to fly, and if not interfered with too strongly by unusual events or by a deliberate incompetent pilot, it will fly. A helicopter does not want to fly."

hel·i·cop·ter/ˈheliˌkäptər/ Noun: A collection of spare parts flying in tight formation.

[RN]

I think PFCAJ was just stating that a "walk around" would have caught this before the dive-- it would have been a quick fix and the safety scooter would have been used.

The issue with this particular scooter was a loose screw that apparently stayed tight enough during the predive checks. Actually, it was probably during those checks that it began loosening even more and then after a 90 minute tow it came loose enough to finally come all the way out when I hit the trigger at the end of the dive.

"The thing is, helicopters are different from airplanes. An airplane by its nature wants to fly, and if not interfered with too strongly by unusual events or by a deliberate incompetent pilot, it will fly. A helicopter does not want to fly. It is maintained in the air by a variety of forces and controls working in opposition to each other, and if there is any disturbance in this delicate balance the helicopter stops flying, immediately and disastrously.
"There is no such thing as gliding helicopter!"

Yep, 3 people just died in Tucson, AZ when the rotors just stopped turning suddenly. This was a medivac crew heading back to base. The pilot was able to maneuver the helicopter away from a house and into the fence surrounding the house instead, but the 3 people on board all died. The only difference was the guy in the house didn't get injured.

[DA Aquamaster]

hel·i·cop·ter/ˈheliˌkäptər/ Noun: A collection of spare parts flying in loose formation.

Fixed it for ya...

[Slüdge]

The issue with this particular scooter was a loose screw...

That's the issue with most of my cave dives.

[PfcAJ]

I am not a big believer in burn testing as it tells you very little about trends and is itself pretty hard on the battery. It's also pretty meaningless unless you actually know how many amps our motor pulls under various conditions. I do use a data logger to monitor battery performance during the dive and I also use it during the charge. So far I've gotten ample warning of a battery that is starting to go south as it's performance starts to sag before a cell fails completely.

I use burn testing data all the time. When your dives involve multiple scooters, or caves where you actually need the scooter to get out, the game changes a bit. You need to know that burntime. In the water isn't the place for surprises. I've caught cell failures in Nickel packs before, too. Its a good thing to know, even if it stresses the pack a bit (which is replaceable and I'd rather stress it than have it stress me