Cambridge 302 Gear/Airbrake Warning - How to Test?

On Sep 9, 5:23*pm, ContestID67 wrote:
I was informed (and verified) that there is a way to easily test the
302 warning system while on the ground.

- Power down the 302
- Unlock the airbrakes with the gear unlocked/up
- Power up the 302

The alarm will then sound (euro siren) after the self test is
complete. *A large upwards pointing arrow will appear in the display,
different than the small speed up/down arrows, meaning I suppose that
your gear is up. *You can silence the alarm by pushing the button.

Yet another undocumented feature/sound from the Cambridge 302!

- John


The power up alarm sounds with brakes unlocked with the gear DOWN and
locked.

After power up test execution the gear warning is as expected - the
gear alarm only sounds if the brakes are unlocked and the gear is not
down locked.

The alarm may also sound on power up with the brakes unlocked and the
gear not down and locked but I can't be sure of that as my assembly
routine has gear down and glider pushed back from trailer before the
batteries are fitted.

Andy

What about the guys who routinely, and with knowledge, begin takeoff with
their spoliers partially opened. I do that when I'm flying the rented LS-4
as it feels to me like it improves aileron control early in the takeoff
roll. I close and lock the spoilers as soon as control is assured. In my
Mosquito, I begin takeoff roll with flaps full negative as I did in my
previous LS-6. Would you deny me a hookup even after I announced to you
that my spoilers are open and why?

I'm talking about the (apparently) sleeping pilots who, at 200 feet fail to
notice that the spoilers have just popped open without command. I've read
of the tow pilot taking that glider pilot to safe altitude, releasing him
within good landing position, and then watching him fail to reach the
airport because he never recognized the problem. And, please, let's not
start another radio discussion.


"Martin Gregorie" wrote in message
...
On Fri, 09 Sep 2011 09:00:53 -0600, Dan Marotta wrote:

If your spoilers "suck open" and you don't recognize it, you shouldn't
be flying.

Maybe other outfits should adopt my club's new-for-2011 change in launch
procedu the cable is NOT put on unless the pilot announces "Brakes
locked" before asking for 'cable on'.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On 9/9/11 3:56 PM, Martin Gregorie wrote:
the cable is NOT put on unless the pilot announces "Brakes
locked" before asking for 'cable on'.

And if the pilot uses spoilers to get better aileron control at the
start of the takeoff?

Or the wheel brake is on the spoilers and the pilot wants to prevent a
rope overrun?

-Tom

On Sat, 10 Sep 2011 19:39:46 -0700, Tom Serkowski wrote:

On 9/9/11 3:56 PM, Martin Gregorie wrote:
the cable is NOT put on unless the pilot announces "Brakes locked"
before asking for 'cable on'.

And if the pilot uses spoilers to get better aileron control at the
start of the takeoff?

Doing standard UK CBSIFTCBE preflight checks, accepting the cable before
opening the brakes and keeping a hand on the brake lever allows the pilot
to accept the cable with brakes locked, so the confirmation can be made
correctly.

Of course, if you are flying somewhere that doesn't teach a preflight
check which includes opening, visually checking, and then locking the
brakes, doesn't include the checks in every flight under instruction and
which tolerates launches for pilots who skip the preflight check then you
should expect launches with unlocked brakes as well as any consequent
crashes.

Or the wheel brake is on the spoilers and the pilot wants to prevent a
rope overrun?

Totally unlikely on our field, which is, if anything, always slightly
uphill since it has a small hump (on a winch launch the wing runner can
see the winch flashing but the pilot usually can't).

I've only flown on one field where that was necessary, the Wasserkuppe,
and again that's a bit special since you take off downwind and downhill
on a hard runway which is steep enough to require a small wooden wedge in
front of the main wheel to stop the glider running forward while the pilot
(s) get in.

In any case in the UK and other places where the CBSIFTCBE preflight
check is taught the pilot will have cycled the brakes AND DONE A VISUAL
CHECK before unlocking and opening them if the glider needs that for a
successful launch, so the announcement "Brakes locked: cable on, please"
should be redundant.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Sep 8, 12:09*pm, ContestID67 wrote:
*If so, how
can I test this system on the ground? *Anyone else install this system
and have any experience? * This weekend I will experiment to see if
the 302 programming is smart enough to allow testing while I am
standing still.

Thanks, John DeRosa

To test the warning just turn on the 302 with the brakes unlocked and
the gear up. Mine sounds most times I rig the glider. To cancel it
press the 302 knob, or lock the brakes, or lower the gear.

The gear warning does not depend on either airspeed or ground speed,
only the warning for unlocked brakes with gear down does.

Andy

On Sep 8, 12:09*pm, ContestID67 wrote:

Reading from the above it would seem that the alarm system is totally
inactive until the GPS indicates I am moving 25+ knots. *If so, how
can I test this system on the ground? *Anyone else install this system
and have any experience? * This weekend I will experiment to see if
the 302 programming is smart enough to allow testing while I am
standing still.

The 302 gear warning is fully functional on ground at zero airspeed
and ground speed. It will also sound when the 302 is powered up with
brakes unlocked even if the gear is down and locked. To cancel it
press the knob or lock the brakes.

My gear warning sounds nearly every time I apply power after rigging
the glider as the brakes have to be unlocked for assembly.

For standard class glider using airbrakes for roll control on takeoff
the warning may sound briefly before it becomes time to lock the
brakes.

As has been mention by others, the brake switch should detect the
difference between "closed and locked" and "closed". Unless the gear
won't stay down if not locked, the gear switch should detect the
difference between "down" and "down and locked". (28 gear floats
halfway if not locked up or down so detecting full forward is
sufficient)


Andy

On Sep 8, 12:09*pm, ContestID67 wrote:
I am in the midst of a project to install a gear/airbrake warning
system on my glider based on the built-in capability of my Cambridge
302. *This system is better than the simple "airbrakes open, gear up"
warning system (http://www.wingsandwheels.com/pdf/gear%20warning.pdf)
as it also alerts the pilot to "airbrakes open on tow".

My "sensors" will be strategically placed reed switches and associated
magnets (and tefzel wire of course). * My primary question revolves
around how to do a pre-flight test of the system.

From the manual...

"Warnings depend on presence or absence of airspeed as well as the
switch contacts. Here
is the logic: Unlocking the airbrakes connects pin 7 to ground. When
airspeed rises above 25 knots, the
alarm sounds. The alarm is cancelled when the airbrakes are locked.
During flight with the
landing gear retracted, unlocking the airbrakes connects pin 7 to
ground and sounds the
alarm. Lowering the landing gear opens the connection between pin 8
and ground and
cancels the alarm."

Reading from the above it would seem that the alarm system is totally
inactive until the GPS indicates I am moving 25+ knots. *If so, how
can I test this system on the ground? *Anyone else install this system
and have any experience? * This weekend I will experiment to see if
the 302 programming is smart enough to allow testing while I am
standing still.

Thanks, John DeRosa

Launch, release from tow, open spoilers with gear up, listen for
warning horn.

On 9/9/2011 8:23 AM, glidergeek wrote:

Reading from the above it would seem that the alarm system is totally
inactive until the GPS indicates I am moving 25+ knots.

I believe the 302 uses airspeed, not GPS ground speed, to do the
measurement.

If so, how
can I test this system on the ground? Anyone else install this system
and have any experience? This weekend I will experiment to see if
the 302 programming is smart enough to allow testing while I am
standing still.

Thanks, John DeRosa

Launch, release from tow, open spoilers with gear up, listen for
warning horn.

That only tests the gear warning, which can also be done on the ground
with the fuselage in the trailer dolly and the gear up.

To test the "spoilers unlocked" warning, the airspeed must increase past
25 knots while the spoilers are unlocked, and once you have released
from tow, the airspeed won't do that.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl

On Sep 9, 2:50*pm, Eric Greenwell wrote:
On 9/9/2011 8:23 AM, glidergeek wrote:

Reading from the above it would seem that the alarm system is totally
inactive until the GPS indicates I am moving 25+ knots.

I believe the 302 uses airspeed, not GPS ground speed, to do the
measurement.

*If so, how
can I test this system on the ground? *Anyone else install this system
and have any experience? * This weekend I will experiment to see if
the 302 programming is smart enough to allow testing while I am
standing still.

Thanks, John DeRosa

Launch, release from tow, open spoilers with gear up, listen for
warning horn.

That only tests the gear warning, which can also be done on the ground
with the fuselage in the trailer dolly and the gear up.

To test the "spoilers unlocked" warning, the airspeed must increase past
25 knots while the spoilers are unlocked, and once you have released
from tow, the airspeed won't do that.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarmhttp://tinyurl.com/yb3xywl


Well, you could try the following at altitude. Theoretically it should
work. Lower gear, pull up hard enough to stall with no airspeed
showing, unlock brakes/spoilers at the stall break. Alarm should sound
when gaining speed during the stall recovery. Although the OP wants to
be able to test on the ground. That's the way I would test as well.

I have a method for testing my pnuematic lines (static, pitot, te). Go
to any pharmacy and get a syringe (without needle) in the smallest
diameter they have. My local pharmacy gives them to me for free. The
real small narrow ones allow for moderate plunger movement without
fear of damaging your instruments. That's not to say you shouldn't be
extremely careful. The point is the really small diameter syringes do
not move much volume. I keep one in my field box with a piece of
surgical tubing attached for testing. It would be perfect for
connecting to the pitot and applying a small amount of pressure to
test the 302 alarm. Not to mention the ease in which it allows one to
test for leaks throughout the rest of the ship.