Cambridge 302 Gear/Airbrake Warning - How to Test?

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


"Mark" wrote in message
...
If your airbrakes "suck open" after you are going faster than 25 knots
it will not warn you, just FYI...

It would work a tad better if the "spoiler open on tow" worked until
the first "gear up" condition before it reverted to the "spoiler
open / gear not down" mode.

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.

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

But those pilots clearly are flying. And are killing themselves and
hurting passengers etc.in depressingly familiar accidents.

In the case of the C302 (and hopefully ClearNav vario) this feature
works very well and I would connect in any glider I owned. The limit
with these things is does having a lots of these alarms just end up
confusing/distractions and can the pilot handle and respond to the alarm
(and given how far behind the aircraft some seem this may be a problem).
But a "it's there problem" attitude and just sitting by while pilots
kill themselves is not going to help this sport or those pilots. And yes
if somebody is clearly having problems with safe spoiler
operation/handling emergencies/distractions etc. my first call would be
time with a good instructor not add a gadget but those gadgets may have
a place as well.

Darryl

I've been using my 302 warnings this way since I've owned mine. Works
very well. As stated, it's simple to test the gear up/brakes unlocked
while on the ground. The speed-enabled warning requires simulated
airspeed. I don't really test the latter feature very often. My pre-
flight checklist handles making sure the brakes/spoilers are locked on
take-off. My ship has a very solid over-center lock mechanism. They've
never unlocked on me without me explicitly doing it to apply brakes/
spoilers. My pre-landing checklist also covers the gear deployment
before brake/spoiler usage for landing. I've actually never had the
alarm go off because I missed something or the brakes/spoilers
unlocked on their own. There were a few occasions where I deployed
spoilers to stay out of a cloud at the top of some strong lift. That's
the only time I've heard the alarm in flight. Hopefully it stays that
way. It certainly gives piece of mind to know I won't land gear up.

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 9/9/2011 8:00 AM, Dan Marotta wrote:


"Mark" wrote in message
...
If your airbrakes "suck open" after you are going faster than 25 knots
it will not warn you, just FYI...

It would work a tad better if the "spoiler open on tow" worked until
the first "gear up" condition before it reverted to the "spoiler
open / gear not down" mode.

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

I gotta say, that's a little harsh. I've had mine open twice, and
another time they were unlocked but I noticed it half way through the
tow before they opened. I did recognize it, but not right away. These
incidents happened over 3000 flight hours ago, and I had over 1500 hours
before any of them happened.

I know 13 (thirteen!) ASH 26 E pilots that have taken off with unlocked
spoilers that sucked open, and they did not notice it right away,
either. Every one of them was a very experienced pilot in airplanes,
gliders, or both. Most had at least 1000 glider hours, some were
competition pilots and National record holders, and all were competent
cross-country pilots whose names you often see on the OLC.

This illustrates what many have noticed: it isn't just the students, the
low-time pilots, or the poorly trained that can make mistakes. I do
think it's important how a pilot responds to prevent a problem from
recurring. All the pilots I've mentioned took steps to improve their
procedures, many also installed "Piggot Hook" devices and/or an
"unlocked spoiler" warning systems.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
you need to know tinyurl.com/yfs7tnz

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.

On Sep 9, 10:00*am, "Dan Marotta" wrote:
If your spoilers "suck open" and you don't recognize it, you shouldn't be
flying.


Well Dan,

What if the pilot locked the spoilers as part of their using a written
pre-takeoff checklist. Maybe, the detent mechanism was slowly failing
and the first sign of this progressive failure was the first time the
spoilers opened on tow. Maybe they opened in conjunction with some
turbulence after the tow was well under way. Maybe the climb rate was
still 3-400 FPM all the way to release. Do you still agree with your
statement??

Mark

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 |

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