Emergency instrumentation for cloud encounters

On Tue, 21 Apr 2015 18:55:53 -0700, mark821ac wrote:

How do you guys avoid midairs when climbing in cloud? Does everyone
circle left? I can't see even Flarm saving you.

1) FLARM still works in cloud, so when you're close under one with no
gliders in sight but FLARM shows a glider above you, that is a
pretty good clue.

2) You should make a radio call on the XC/cloud flying frequency[1]
giving your intentions and position. Anybody else who is nearby
should respond with their details. If FLARM shows a glider above
you in cloud, frankly you're an idiot if you don't make that call
before switching on the T&B etc.

3) Clouds are much bigger than gliders so the chances of a collision
are relatively low (the big sky theory of collision risk): its
your choice whether you take that risk or stay out of cloud.

[1] In the UK 130.4 MHz is reserved for XC message passing and cloud
flying. I don't know if other countries have similar arrangements.


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

On Wednesday, 22 April 2015 14:58:44 UTC+3, Martin Gregorie wrote:
One question: I haven't tried this, but my guess is that a mechanical T&B
will come up showing the correct reading if it is switched on while
turning. It will do this because what it shows is the amount a spring is
deflected by the precession force a gyro applies to it when the aircraft
yaws. Am I right in thinking this?


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

Yes it will indicate rate of turn even if switched on during thermalling. There is always horizontal acceleration during turning, and gyro indicates only this as rate of turn. However being used to temperamental 50-something years old T&B's I might wan't to check gyro action well before entering cu-nim (got to admit that I've flown into smaller clouds switching gyro on "on the fly" just before entering cloud). I think it takes 15-30 secs to achieve stable gyro rotation, or little bit less with LiFePo4 battery as these old things seems to like little extra voltage compared to lead acid batteries.

I think the less training and/or currency in instrument flying a pilot has, the more he is going to find an artificial horizon to work better for him than some sort of turn rate indicator.

The inputs required to break a well-developed pitch phugoid without the aid of an artificial horizon, are counterintuitive.

But most important lesson that the pilot must learn is that must be prepared to utterly and completely believe the instrument, against what his senses are telling him. He must expect to be disoriented. I don't think it takes all that much training to deliver that lesson, so long as the training is truly effective. Which probably means, conducted in actual cloud!

Flying "partial panel", in my experience it's normal to be disoriented much of the time. Maybe this would no longer be the case if I had more practice at it.

S

With all due respect to the poster below who argues the big sky theory applies to clouds (or anywhere for that matter). While not a highest time pilot, I have multiple thousands of hours between gliders, airplanes and helicopters I have actually swapped paint once with another aircraft and have at least 10 near collisions (20 feet or less of separation). Three times were while ATC was providing separation! One time is a story in itself and only a miracle/angel kept it from being a tragedy that would have killed 110 people (this one was on take off, same controller cleared two aircraft to fly into each other). I am not a big fan of the big sky theory, I frankly think it is as out dated as Flat earth.



On Wednesday, April 22, 2015 at 5:16:31 AM UTC-7, Martin Gregorie wrote:
3) Clouds are much bigger than gliders so the chances of a collision
are relatively low (the big sky theory of collision risk): its
your choice whether you take that risk or stay out of cloud.

[1] In the UK 130.4 MHz is reserved for XC message passing and cloud
flying. I don't know if other countries have similar arrangements.


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

On Wed, 22 Apr 2015 06:21:14 -0700, krasw wrote:

Yes it will indicate rate of turn even if switched on during
thermalling. There is always horizontal acceleration during turning, and
gyro indicates only this as rate of turn. However being used to
temperamental 50-something years old T&B's I might wan't to check gyro
action well before entering cu-nim (got to admit that I've flown into
smaller clouds switching gyro on "on the fly" just before entering
cloud). I think it takes 15-30 secs to achieve stable gyro rotation, or
little bit less with LiFePo4 battery as these old things seems to like
little extra voltage compared to lead acid batteries.

Thanks for that confirmation.

My T&B was already modified for glider use when I bought it. This meant
that its rate marks indicate a 30 second turn (nice for thermalling) and,
as it is a 28v instrument, it came with a solid state DC-DC converter so
it will run off a 12v battery. It comes up surprisingly fast: I haven't
timed it but would estimate 10-15 secs to come up to constant speed.

When first installed, it kicked up a nasty row on the radio that ferrite
cores didn't fix. What did work was installing a 500 uF electrolytic
capacitor across the 12v input to the DC converter. This is a special
capacitor designed to prevent electric motor noise from affecting other
kit on the same power rail. IIRC it is rated at 35v and 1.5 amps.


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

PS one instance where an artificial horizon would really win hands-down over a turn rate indicator, is if the pitot tube ices up. Has this ever happened to you (anyone?) I've had the yaw string freeze to the canopy, but don't think there was much ice elsewhere on the glider.

S

I'll go back and quote.....

"I will let my superior judgement keep me from using my superior skill in a situation...."

Enough said.

After that, it's a toss-up, I would not want to place bets.

To answer all the speculation on what the characteristics of the new solid state artificial horizons, here are what the factory says about the LX Nav S80.

Question: Can you provide an explanation of the performance standards?
Answer: The internal sensors and software can respond at +/-90 degrees/sec. The internal gyro can measure up to 2000 degrees/second which is 6 revolutions/second.

Question: Any limitations on aircraft position or rate of movement?
Answer: No. There are no limitations when used in a glider.

Question: Can the unit lose orientation and "tumble" like a mechanical unit?
Answer: No. It's not like a conventional gyro. It recovers from any position.

These units are always on and always registering the aircraft orientation. Switching to the artificial horizon screen just activates the display.

I fully understand that the workings of the vario-associated AHRS-driven artificial horizon units are "always on". Just as a point of curiosity, I wonder how long it would take to get an accurate reading on this type of artificial horizon if you powered up the whole system from a cold start while engaged in a steep-banked turn.

No practical ramifications really, at least if the unit is for emergency use only-- system failure isn't a big concern in this context. I'm just curious.

Meanwhile, for those pilots flying with simpler instrumentation wanting something for purely emergency use, or for those pilots engaged in intentional cloud flying where there is a legitimate need for some sort of back-up system for redundancy, I still suggest-- consider the self-contained piezo-electric turn rate indicator I linked to on my first post.

S

I fully understand that the workings of the vario-associated AHRS-driven artificial horizon units are "always on". Just as a point of curiosity, I wonder how long it would take to get an accurate reading on this type of artificial horizon if you powered up the whole system from a cold start while engaged in a steep-banked turn.

No practical ramifications really, at least if the unit is for emergency use only-- system failure isn't a big concern in this context. I'm just curious.

Meanwhile, for those pilots flying with simpler instrumentation wanting something for purely emergency use, or for those pilots engaged in intentional cloud flying where there is a legitimate need for some sort of back-up system for redundancy, I still suggest-- consider the self-contained piezo-electric turn rate indicator I linked to on my first post.

S