Sxmarbury33 From United States of America, joined Oct 2000, 445 posts, RR: 0 Reply 1, posted (11 years 6 months 3 weeks 5 days 10 hours ago) and read 16636 times:
The GPWS callout sink rate is when the aircraft is approaching the ground faster than it should be in normal service. This is probably the most frequent alert because its just a matter of a few hundred feet persecond. If this is not corrected you may get the terrian and or pull up warning. The dont sink warning is mainly for after takeoff. If the GPWS senses from the RA that the aircraft is decending after the takeoff it will give an aural call out to warn the pilot.
XFSUgimpLB41X From United States of America, joined Aug 2000, 4104 posts, RR: 38 Reply 6, posted (11 years 6 months 3 weeks 5 days 9 hours ago) and read 16541 times:
To further clarify what has been said.. sink rate has to do with the vertical speed of the aircraft. It's easy to get this in a windshear situation after departure or on arrival- the Don't Sink warning comes in when your sink rate has a projected danger of sending you dancing with a hill. I've only heard on departure on a 2 engine failure the DC-10... the most ive heard it is adjusting when coming off of a non-precision approach or visual approach and trying to get the airplane set up for a stabilized final descent. When i first heard the warning, i also thought it said Don't Think.
All of these modes have specific aural warnings associated with them which are issued based on specific aircraft performance parameters.
The "SINK RATE" callout is associated with Mode 1 only and is issued when the GPWS detects excessive descent rate for the altitude above ground. It is followed by "PULL UP" at a pre-determined point.
The "DON'T SINK" callout is associated with Mode 3 only and is issued when the aircraft sinks after takeoff. The altitude loss at which the callout is issued is dependant on the height above ground. This mode is inactive above 1500 feet.
MD11Nut From , joined Dec 1969, posts, RR: Reply 8, posted (11 years 6 months 3 weeks 5 days 4 hours ago) and read 16485 times:
Someone here seems to take the attitude that these cautions and warnings are nothing but nuisance...I wish you wouldn't take it too slightly.
Perhaps with the exception of Mode 3, "Don't Sink" and occasionally some nuisance alerts, any of the GPWS warnings could literally mean you are seconds from being a grease spot on some hills. I wouldn't turn it off if I were you.
I was on about half a dozen of GPWS flight tests and my impression was that these warnings were darn hard to get. When we get them I'd still remember the chills that ran down my spine, thankful that we were inducing these warnings on purpose. As I recalled, to get Mode 1 "Sink Rate" and the subsequent "Whoop Whoop Pull Up", we had to start out at 2500ft AGL diving straight at the ground at about 3000fpm. It's normal to pull 2.5g in the pull up maneuver. Quite an exciting ride in retrospect. Unless you fly a Dash 8 doing 6 degree path descents at high altitude with high ground speed, if you hear this in real life, better arrest that rate quick. You'd get less than a minute to live, usually.
To test Mode 2, we aimed at a mountain, flying about 200 ft above the top. Because it's Radar Altimeter based, you'd get the "Terrain Terrain" about 15 seconds before impact, the "Whoop Whoop Pull Up" about 10 seconds before impact (if you happen to fly below the peak). You hear this, you immediately aim for the moon. The Cali, Columbia accident in 1995...the airplane got the warning 12 seconds before it hit the mountain. Yes, that was a Mode 2. The Enhanced GPWS (TAWS) would give you about 60 seconds caution (Terrain) and 30 seconds (PULLUP).
Mode 3 was easy to get, takeoff, lose about 80 ft altitude or get a negative climb rate of more than a 100fpm or so then you get it.
To get Mode 4, I remembered you have to be really close to the ground about 500 ft AGL or so before you get "Too Low Terrain", keep getting closer then you get "Too Low Gear" then about 200 ft AGL or so you'd get "Too Low Flaps". We'd pick some flat field out in the desert to do this test. All I would see would be brown earth all around us. I'd hate to run into some high voltage power lines out there.
Mode 5 "Glideslope" wasn't too bad but you have to be a whole dot below glideslope really close to the ground (about 300 ft AGL or so) before you'd get it. I'd react quickly to any of these.
If you are lucky enough that the aircraft you fly has it, use it. Don't turn it off. It could save your life some day. I read somewhere that 70% of all accidents out there are due to one form of CFIT (controlled flight into terrain) or another. A few airliners CFIT accidents happened partly because the crew didn't react to GPWS Pull Up warnings aggressively.
The cheapest GPWS out there is about $8,000 and unfortunately it's not required for part 91 unless the a/c has 6 pax seats or more. So most GA aircraft out there do not have this gem installed. Hopefully it'll get much cheaper really soon.
PPGMD From United States of America, joined Sep 2001, 2453 posts, RR: 0 Reply 10, posted (11 years 6 months 3 weeks 4 days 22 hours ago) and read 16436 times:
Well the PC-3 that I have flown on a couple of occasions has an old military one installed in it, way too much of a distraction in a two seat aircraft. It went off constantly while I was in the pattern, maybe the ones in the airliners are a lot better but this one was just plain annoying in a situtation where I had everything under control.
FDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 37 Reply 11, posted (11 years 6 months 3 weeks 4 days 20 hours ago) and read 16421 times:
I view the GPWS as a data consolidater. The GPWS in itself takes data (radio altitude, baro altitude, vertical speed, gear position, flaps, etc) available to the pilots, integrates it, and contructs a picture of potential danger. A valuable system. And now with EGPWS, even better.
EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2 Reply 12, posted (11 years 6 months 3 weeks 4 days 19 hours ago) and read 16408 times:
"It's easy to get this in a windshear situation after departure or on arrival" would trigger an audible "Windshear" warning on a part 121 airliner in an arrival or departure configuration, not "Sink Rate".
Wind Shear warnings have a higher aural priority that GPWS or TCAS.
Avt007 From Canada, joined Jul 2000, 2132 posts, RR: 5 Reply 14, posted (11 years 6 months 3 weeks 4 days 15 hours ago) and read 16361 times:
False alarms are a fact of life with gpws. No doubt as newer systems come on line, it will improve, but complacency can be a problem. I worked on gpws snags for 15 years, and false alarms are very common. The biggest problem is everything surrounds the rad alt. The dash8 has lots of snags with these, resulting in terrain warnings in cruise, pull up warnings while taxiing in the rain, too low gear @ 20,000 feet. I can't say as I blame the crews, but hopefully they'll react fast if it's IFR.
Airplay From , joined Dec 1969, posts, RR: Reply 15, posted (11 years 6 months 3 weeks 4 days 8 hours ago) and read 16313 times:
With respect to your "correction":
Although windshear detection is a requirement for Part 121 operations, you need to remember that there are other types of operators who do not require it. As a matter of fact a great deal of business aircraft with GPWS or EGPWS/TAWS don't have this option enabled or another form of windshear detection installed. Therefore, in these instances you may in fact get a "SINK RATE" in windshear conditions.
XFSUgimpLB41X From United States of America, joined Aug 2000, 4104 posts, RR: 38 Reply 18, posted (11 years 6 months 3 weeks 4 days 7 hours ago) and read 16298 times:
I very well could have been confused as to what the GPWS was saying when... I havent had the formal ground school in the 10, just have been taught the SOPA and SMAC and international operations in them... there is a mode check during my preflight flows on the GPWS (which had been upgraded to EGPWS last time i was in there) and i remember it going through all those callouts... just not in that order. When the thing went off i generally was too busy, and just remember it yelling at me about something. I remember a windshear and sink rate callout very close together.... probably was the one on approach from what these modes have been. Also the dont sink one, I suppose that was on the depature windshear, as i have been trained in all the most violent profiles they give the students. The windshear alert always gets called out in the event of one... the other items will follow.
Wilcharl From United States of America, joined Jun 2000, 1158 posts, RR: 3 Reply 20, posted (11 years 6 months 3 weeks 4 days 6 hours ago) and read 16291 times:
I think essentialpower thinks that XFSUgimpLB41Xh got his king air "type raiting" (yes i know the king air doesnt require a type raiting, but someone that went there said they had one but anyways... )from Tab aviation in Deadland florida
XFSUgimpLB41X From United States of America, joined Aug 2000, 4104 posts, RR: 38 Reply 21, posted (11 years 6 months 3 weeks 4 days 6 hours ago) and read 16289 times:
Basically i was agreeing with you, Essential... 121 planes have the windshear mode enabled. Plus i was clarifying that i have not had the groundschool for the DC-10 and the EGPWS...just been through the flight sim portion of training in standard and emergency operating procedures.
I'm typing a 10 page paper and using this site to procrastinate... my responses probably aren't as coherant tonight.