View Full Version : TB20 gear warning
28th Jan 2012, 10:10
This isn't Peter's plane I hope? :)
Two Guys Crash Plane Despite Alarm - YouTube (http://www.youtube.com/watch?feature=player_embedded&v=Hs5ChcYbaNU#!)
28th Jan 2012, 10:21
Not me :)
That video has been well discussed in various places.
The plane is externally identical to mine except I have a 3B prop. I think theirs was an early GT (year 2000 or so) because the avionics look a bit of an odd mix.
Hard to know what to make of it - other than one should not disregard warning noises without knowing exactly what one is doing.
There are two gear warnings: a horn goes off if the full flap is selected and the gear is still up, and it goes off if the throttle lever is below a specific position and the gear is still up.
You can defeat the first warning by landing with takeoff flap (which is pointless, contravenes the POH, but is reportedly popular in the USA where they have lots of big runways) and you can disable the second warning by landing into a strong headwind which requires a lot of power. The lesson, therefore, is to always use landing flap. Then you should never get any warnings, and getting any should mean a go-around because it is either a gear-up or a stall.
These people were correctly configured but simply ignored the noises.
Mind you, if the actual CVR of AF447 ever leaks out, I am sure we will hear something very similar...
28th Jan 2012, 10:35
The Cessna TR182 got the same warning system basically. Unfortunately, there is no certified method to connect it to the audio panel. The better the ANR headsets get, the less audible the gear warning becomes.
Ideally I would like to install something like this (http://www.p2inc.com/audioadvisory.asp) but I haven't found any EASA approved products.
Regarding no flap landings, over here when you want to land at a very busy airport where they always have 3-4 planes on the ILS, you only get your chance when promising 120-130KTAS on short final which means no flaps, quite some power and gear up until shortly before threshold. Often they also tell you to touchdown in a specific area so you can leave the runway quickly. When IFR, they also like to give you special instructions for a missed approach (basically omitting the mile long straight leg). No time for checklists in any of this.
28th Jan 2012, 11:14
I don't think my warnings go into the intercom either (would have to check the circuits to be sure). It's just a loud speaker.
That's an interesting box. I wonder how they actually sense the gear position. What about the recent FAA-EASA treaty for mutual acceptance of test data? Very little is said of it but it may mean some kind of mutual acceptance of STCs as Approved Data.
It is not unreasonable to fly the ILS at Vlo all the way to the FAF, and slow down to Vs2 in the last bit of the ILS, and go to full flap on the last bit, basically at 200ft. Having an autopilot helps enormously with that, of course, otherwise you are like a one armed bandit, retrimming etc. The 737 behind you is definitely on autopilot and autothrottle ;)
28th Jan 2012, 11:52
Our venerable Arrow still has (they were disabled in later models and then removed altogether) the Auto extend feature in which, if the manifold pressure is reduced to, or the airspeed drops to, pre landing values, a klaxon loud enough to wake the dead sounds, warning that the gear is not down.
On our Arrow, both the stall warner horn and and auto extend horn are loud enough to break through the best ANR headsets.
(Indeed on the ground, when preflighting, the stall warner can be heard 50 yards away from the aeroplane).
Then, if you ignore the klaxon , the gear drops automatically in pretty short order, so technically at least, it should be impossible to land with the gear up.
Later models had a pin which locked this feature, but an amber light on the panel, just above the u/c green indicator bulbs, flashed intermittently all the time the pin was engaged. This I think was sufficiently annoying for Mr Piper to remove the autoextend feature.
I think it is a bl oody good idea to have auto extend: fortunately 'it never happened to me' while landing but it scared the cr ap out of a wet behind the ears AFI who had never flown an Arrow when he was doing my 2 yearly check flight:
Despite my telling him to hold the auto extend lever up while doing stalls and slow flight, he said 'no it'll be alright' >
So when we approached the stall with the stall warner blaring, the additional klaxon sounded and the gear came down with a thump: I had to lower the nose smartly because of the extra drag effect on stalling speed, and it was all too much for him.
The only serious moment when auto extend would be a BAD THING would be on ditching: Sudden unexpected appearance of the gear just before hitting the water could seriously spoil your day.
So, when flying over water RHS pax is shown the gear extend lever just above the flap handle and briefed, if ditching required, to haul it up with all his might until we are nicely bobbing on the waves.