Linden Accident - Question about "Droop Lock"

[Bob Chilcoat]

I was talking to a Sikorsky pilot at our airport about this accident:
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20050926X01530&key=1

He said that Sikorskys have a "droop lock" in the cockpit that should
prevent the rotor from getting too low. How does this work? Does it leave
a certain amount of positive AOA in the blades so that they "fly" a bit
higher? I was curious.

Talking to my neighbor who runs a large helicopter concession on the Hudson,
and who keeps his ships at Linden (this was not one of his), the line boy
was very tall, and that presumably contributed to the accident. At any
rate, he's very lucky to be alive.

--
Bob (Chief Pilot, White Knuckle Airways)

[Jim Carriere]

Bob Chilcoat wrote:
> I was talking to a Sikorsky pilot at our airport about this accident:
> http://www.ntsb.gov/ntsb/brief.asp?ev_id=20050926X01530&key=1
>
> He said that Sikorskys have a "droop lock" in the cockpit that should
> prevent the rotor from getting too low. How does this work? Does it leave
> a certain amount of positive AOA in the blades so that they "fly" a bit
> higher? I was curious.
>
> Talking to my neighbor who runs a large helicopter concession on the Hudson,
> and who keeps his ships at Linden (this was not one of his), the line boy
> was very tall, and that presumably contributed to the accident. At any
> rate, he's very lucky to be alive.

Are you sure he didn't say "droop stop?" Those are centrifugal
weights on springs that keep the blades from flapping too low. In
general, they move between idle and 100% rotor rpm (so the blades
have freedom in flight but are limited to a safe height when you are
idling on the ground, especially when shutting down). When they move
into place, they physically stop the blades from flapping too low,
like putting a wedge in the hinges of a door.

Sometimes they get dirty and don't move when they should...

A few other names for the same or similar devices might be antiflap
restraint, static stop, or something along those lines. I don't know
exactly what they're called on the S-76.

[Dave S]

WHen i was a child and teen, and dad was a chopper jockey, he drilled
one point into my head. Never EVER approach an S76 from the front.
ALWAYS the sides.

Dave

Bob Chilcoat wrote:
> I was talking to a Sikorsky pilot at our airport about this accident:
> http://www.ntsb.gov/ntsb/brief.asp?ev_id=20050926X01530&key=1
>
> He said that Sikorskys have a "droop lock" in the cockpit that should
> prevent the rotor from getting too low. How does this work? Does it leave
> a certain amount of positive AOA in the blades so that they "fly" a bit
> higher? I was curious.
>
> Talking to my neighbor who runs a large helicopter concession on the Hudson,
> and who keeps his ships at Linden (this was not one of his), the line boy
> was very tall, and that presumably contributed to the accident. At any
> rate, he's very lucky to be alive.
>

[Darrel Toepfer]

Dave S wrote:

> WHen i was a child and teen, and dad was a chopper jockey, he drilled
> one point into my head. Never EVER approach an S76 from the front.
> ALWAYS the sides.

I was riding them in the late 70's and early 80's when AirLog used them
in the gulf, they are sweet. I'd have to agree and add the A-Star to the
list as well, heard story once that the OAT probe was sheared from an
A-Star by blade dipping (droop)...

[Simon Robbins]

"Bob Chilcoat" > wrote in message
...
> I was talking to a Sikorsky pilot at our airport about this accident:
> http://www.ntsb.gov/ntsb/brief.asp?ev_id=20050926X01530&key=1

Another one at the weekend, this time in an S300:

From the Adelaide Advertiser:

Pilot walks into chopper blade

04oct05

A 58-year-old Queensland helicopter instructor is in a serious condition
after walking into a slowly revolving rotor blade.

The pilot - with more than 30 years experience - works at Becker Helicopters
which is based at the Sunshine Coast Airport at Maroochydore.
He had just completed a training flight in the two-seat Hughes 300 chopper
when the accident happened at 9.20am (AEST) today.

Police said he had shutdown the chopper, removed his helmet and was walking
away when he was hit on the head by the slow moving main blades.

The pilot received a compound fracture to the skull and was rushed by the
Energex Community Rescue Helicopter to the Royal Brisbane Hospital in a
serious condition.

Becker Helicopters chief executive Jan Becker said the man was from the
Sunshine Coast and had worked at the company for three years.

"It's just one of those things," she said.

Mrs Becker said staff and trainees were receiving counselling.

Energex pilot John Hodges said the blades were moving between 20 and 30
revolutions a minute when the accident occurred.

"He was lucky the blades were moving relatively slow," he said.

"Had they been going at full speed it would have been all over for him."

[[email protected]]

On Tue, 04 Oct 2005 11:15:33 -0500, Darrel Toepfer
> wrote:

>Dave S wrote:
>
>> WHen i was a child and teen, and dad was a chopper jockey, he drilled
>> one point into my head. Never EVER approach an S76 from the front.
>> ALWAYS the sides.
>
>I was riding them in the late 70's and early 80's when AirLog used them
>in the gulf, they are sweet. I'd have to agree and add the A-Star to the
>list as well, heard story once that the OAT probe was sheared from an
>A-Star by blade dipping (droop)...

There is nothing the the cockpit to control the "static lock"/"droop
lock" or whatever the current name is. Because of the amount of
flexability in the longer blades of the bigger helicopters there is a
lock that automatically engages via springs at a preset RPM. It
usually will lock at a lower RPM on shutdown then on start up. If the
lock fails to engage, it is a very real possibility of whacking off
your own tail with the blades. That is one of the main reasons you
will see the crew chief outside the helicopter as he is watching to
make sure the stops do what they are suppose to. If they do not
engage/disengage, there is emergency procedures. The one for shutdown
can be pretty exciting as you have to get the rotor stopped as fast as
possible.

As far as the A-Star, that is a story. The blades would break prior to
that. I have shut down in 40 kt. winds, and although the blades droop
pretty far down, they in no way could hit the cockpit area without
breaking.

[Simon Robbins]

"The OTHER Kevin in San Diego" <skiddz "AT" adelphia "DOT" net> wrote in
message ...

> I hear some of the Kamov coaxial machine's lower mains droop to about
> chest level as they spin down... That could make for a bad day too...

I was looking at an old Westland Wasp last week at Helitech. Standing next
to it your eyes are about level with the rotor hub, and the drooping blades
are at waste height!

Si