jtrain609
Antisocial Monster
DId you guys look up to see if the ERJ is setup the same way? Because this is how we're doing RNAV approaches.
Vertical path non-precision approach safety?
- Thread starter DE727UPS
- Start date
DId you guys look up to see if the ERJ is setup the same way? Because this is how we're doing RNAV approaches.
SpiceWeasel
Tre Kronor
You cannot modify the snowflake in the RJ unless you potentially hand-build an approach using the fix "RWxx" as the final point. All pre-programmed approaches end in elevation RWY which is a fixed non-changeable number.
CoffeeIcePapers
Well-Hung Member
It's certainly safer than a dive and drive, especially with multiple stepdowns.
C150J
Well-Known Member
My schedule is jammed today, but you should also check out the difference between "descent angles" and "glide paths" as listed in the profile view of Jeppesen procedures. Pretty major implications as far as obstacle clearance between the DA/MDA and the runway. Bottom line: if your plate says "descent angle" and lacks a published VPD, the pathway from the MDA to the runway has NOT been assessed for obstacles - no path you fly will 100% protect you. You are expected to maintain visual clearance. This can be a long ways on some mountainous non-precision approaches.
Will only become more critical of a briefing item as EFVS becomes predominant.
Will only become more critical of a briefing item as EFVS becomes predominant.
Polar742
All the responsibility none of the authority
We not only have authorization for VNAV approaches, we can build our own approach as long as we respect MDA. We get to use DH in lieu of MDAs on certain approaches. Actually shooting a non-precision approach in other than VNAV raises our mins to MDA+50'
Even in the VNAV-advisory only jet, you could shoot a constant descent based in the advisory information and a bit of tweaking.
Yes, the old FMC argument. If the information programmed into the box is pulled out of the database, and it matches the chart (same data), it will fly it. If it is less accurate than flying radials, then the electrons on the GPS satellites stopped at Taco Bell for Fourth Meal & our entire navigation is screwed.
Autothrust Blue
Welcome aboard the Washington State Ferries
The 'problem' with dive and drive is that it requires a large change of pitch and thrust/power to level at MDA, followed by another change of pitch and thrust to initiate the visual descent to land. Sometimes you don't have any other viable options for getting in - even on a straight in non-precision approach - but for the most part shooting a nonprecision approach with some sort of vertical guidance, and treating MDA+50' as a decision altitude is a better way to do things, provided you have the equipment to do it.
In the ERJ, we treated the flight path vector generated by the FMS for RNAV approaches as a glideslope. We did not treat arrival at MDA+50' as decision altitude (for whatever reason - really should have).
Of course, you either had to - gasp - hand fly it or bump the VS or pitch knobs in order to stay on the vertical path.
"VGSI and descent angle not coincident." And 'frequently'.
PeanuckleCRJ
Poodle Wrangler
Not food for thought. There is a distinct level of misunderstanding that you have here. Any DPE worth their salt understands that our procedures and systems are certified and we follow specific monitoring criteria as need be; we have flow charts for everything that is not a CAT I ILS.
Most of the arrivals we fly these days are RNAV, so raw monitoring is out the window there, and we are certified RNAV overlay for all non precision approaches, and on virtually all approaches in the states we are certified to fly a VNAV path to a DA. Dive and drive can be quite dangerous on a large jet aircraft with a long spool time... We monitor all crossings on the approach as the VNAV sniffs down.
PeanuckleCRJ
Poodle Wrangler
Here's one that will kick your ass if you're not pre-briefed on it.
Gotta go missed before an "RF" leg? TOGA, then ya better hit LNAV immediately or you're going to "S'cuse me, while I kiss the volcano"!
Fun as hell to fly in the simulator at night, when you'd be flying it, and then turning on the visuals in simulated day VMC to see what you're actually doing.
They'd always give us nasty crosswinds too.
Then "CHECK RNP" or "VERIFY POSITION" would pop up on the FMS head right before an RF leg and hilarity ensues.
One less button push on fifi... We have automatic managed nav coupling on TOGA!
Flying into Quito was always interesting... get in at midnight, fog always rolling in. I was very glad to have RNAV RNP cerification. Every time I flew in, the captain flew it on the HUD on the 737 which reduced the threats a bit more.
jtrain609
Antisocial Monster
We're not allowed to do dive and drive anymore. The company wants us to divert if we can't get in with a CANPA approach if that's all we can shoot at an airport. Dive and drive is not located anywhere in our books now.
Also, the box isn't controlling, the step down altitudes are. The box will keep you at it above those fixes, but they're still controlling.
But even with the box deferred we can do CANPA approaches.
Seggy
Well-Known Member
Serious question for you @Boris Badenov. You have a bunch of guys with a ton of experience telling you very specifically "why dive and drive" isn't what their employer wants them to do for a variety of reasons, the main one is there is a safer way to do it with a vnav path. When you get your dream job, whatever that may be, are you going to develop your 'own ways' to do things as you will be questioning the reasoning behind the solid procedures even when they are explained to you in a rationale way on why things are done that way?
Autothrust Blue
Welcome aboard the Washington State Ferries
Boeing builds airplanes; Douglas builds character.
D
Deleted member 27505
Guest
Did I say anything about shipping poop? IF You show up at NJC with C073 pinned to your little sailor outfit and IF I find your parents to vouch for you, AND IF I find both it and them trustworthy, I'll buy you a Shirley Temple. Because you deserve it, for living this long doin it rong.
See you there, handsome!
Signed,
Cav
Former Maddog Whisperer
Gotta go missed before an "RF" leg? TOGA, then ya better hit LNAV immediately or you're going to "S'cuse me, while I kiss the volcano"!
Don't forget the speed limit too!!
PhilosopherPilot
Well-Known Member
I didn't, but I doubt it's the same given what little I know about your procedures.
PhilosopherPilot
Well-Known Member
Boris, for the CRJ, the procedure was to "dive and drive" to the FAF at 1200 fpm. At .2 prior to the FAF, you start a descent at roughly 800 fpm, or whatever the published rate of descent is for your ground speed (if it has a coded descent angle). That approximates 3 degrees.
You have set in the MDA window (Baro mins) a derived decision altitude of 50 feet above the MDA. When you get there, you go missed, and theoretically never go below MDA.
This is considered safer because:
1. You're not diving at the ground down to low levels.
2. You're descending in a similar manner to the ILS, and if you get the runway in sight, you just continue that approximate descent rate to the landing.
3. You spend less time at the MDA, so you're not driving around at 600 AGL looking for a tower to hit. If you're at the DDA, you go missed.
So for the step downs where cross radials are used, etc., you are using dive and drive, just like the olden days. The advisory VNAV is just that, advisory only. So you don't really need it, and don't trust it. Your only "trust" is that your ground speed should give you the rate of descent you set. Like I said, it's normally about 800 fpm.
Does that make sense?
Aircraft that are more automated do it differently, and with fewer button pushes, I realize that.
You have set in the MDA window (Baro mins) a derived decision altitude of 50 feet above the MDA. When you get there, you go missed, and theoretically never go below MDA.
This is considered safer because:
1. You're not diving at the ground down to low levels.
2. You're descending in a similar manner to the ILS, and if you get the runway in sight, you just continue that approximate descent rate to the landing.
3. You spend less time at the MDA, so you're not driving around at 600 AGL looking for a tower to hit. If you're at the DDA, you go missed.
So for the step downs where cross radials are used, etc., you are using dive and drive, just like the olden days. The advisory VNAV is just that, advisory only. So you don't really need it, and don't trust it. Your only "trust" is that your ground speed should give you the rate of descent you set. Like I said, it's normally about 800 fpm.
Does that make sense?
Aircraft that are more automated do it differently, and with fewer button pushes, I realize that.
Tommay85
Well-Known Member
What I'm getting out of this, is that you guys are basically using your FMS to visually approximate on your screen, what a stable descent down to the MDA would be? Something a smooth pilot in something jurrasic would be doing anyways, but figuring it out on their head instead. Am I right? I'm not sure stopping at 50 feet above does any good though. I've seen 50 feet make a difference in having the required visibility and not when the runway comes in sight. Or can you still go down to the actual MDA? Either way, I'm not seeing what's illegal or unsafe about it as long as the "magic" is keeping you above the minimum altitudes on the plate. I'll read the thread again tomorrow, it's late...
Personally, I do that anyways in all the garbage cans I fly these days. It's how I was taught at the puppy mill. It's smoother too, especially on approaches with a million step downs. The VOR in Tuscon for example. I'd probably throw up if I was riding in the back with the pilot diving to each step down. I've always felt that diving down to the MDA is just asking to get distracted by an outside factor and messing it up anyways, but then again, I've had to go missed a handful of times because I thought wrong on how much room I had to get down due to fatigue or just plain brain fade.
Personally, I do that anyways in all the garbage cans I fly these days. It's how I was taught at the puppy mill. It's smoother too, especially on approaches with a million step downs. The VOR in Tuscon for example. I'd probably throw up if I was riding in the back with the pilot diving to each step down. I've always felt that diving down to the MDA is just asking to get distracted by an outside factor and messing it up anyways, but then again, I've had to go missed a handful of times because I thought wrong on how much room I had to get down due to fatigue or just plain brain fade.
Tommay85
Well-Known Member
Yeah, I didn't see anything that struck out as illegal or unsafe. Just trying to figure out what the debate is about. VNAV is displayed based on your position and that sounds exactly like what your FMS is doing.
Somewhere deep in my brain parts that are full of cobwebs, I remember UND teaching us to use the snowflake(or was it the banana) on non precision approaches as a suggested vertical path in the CRJ sim.
edit: nevermind, the chart daselben posted says it all
Somewhere deep in my brain parts that are full of cobwebs, I remember UND teaching us to use the snowflake(or was it the banana) on non precision approaches as a suggested vertical path in the CRJ sim.
edit: nevermind, the chart daselben posted says it all
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z987k
Well-Known Member
I agree that a constant descent rate is better than dive and drive, although if it's going to be close I want some extra time at MDA to look around.
That said, your #3 is one of the more ridiculous things I've read on the internet today. How on earth are you going to hit anything if you're at or above MDA? You have an absolute minimum of 250ft of obstacle clearance, and possibly a whole lot more... depending on lots of things that terps explains. A non precision approach is not scud running.