G5 Autothrottle question

[G3G4]

When the throttles come to idle at 50 feet rad alt, is that a function of rad alt only or the voice call out "50 ft"

Here's what happened, both times at an airport with 5000 ft or less runway.

On approach we got all normal call outs except for the 50 ft call out and both times the throttles did not retard. I'm trying to figure out if we have an auto throttle problem, rad alt problem etc. Any ideas? Or just a glitch in system. Again the both times this happened was flying into a short runway all other times they worked as designed.

 

[gutshotdraw]

I don't use the auto-retard feature for two reasons:

1) I still fly the G-IV from time to time and don't want to be in the habit of relying on it (remember the G-IV accident at TEB a few years back? Auto-throttles were ON at touchdown).

2) Every time I watch the other guy use it, the airplane floats and lands long. Every time.

As to your question, as I understand it, the radat triggers the auto-retard and the callout so I'm thinking there's a hiccup in the radar altimeter.

 

[fokkerjet]

Radio Altimeter in the G550:

[FONT=Swiss721SWA,Bold][FONT=Swiss721SWA,Bold]

5. Retard Mode​

[/FONT][/FONT]

The retard mode is used to establish a fixed rate of throttle retardation to the idle thrust
position during the aircraft flare on landing. The retard mode is used for AP/FD coupled
and non-coupled approaches, and it is activated based on radio altitude < 50 ft (i.e., gears
down, flaps > 31.5​

​

​

​

_).
When the aircraft touches down, and both throttle levers are located in the idle thrust stop,
the AT automatically disconnects in preparation for reverse thrust. If the aircraft touches
down without the AT retarding the throttles because of a failure to detect a landing
configuration or lack of radio altitude, the AT retards the throttles to the idle thrust position
when touchdown is detected (i.e.,WOWor both wheels spun up), before it automatically
disconnects. The AT remains engaged until touchdown, so it is available in the event of​

a go-around during the flare.

 

[semperfido]

Sounds like a problem in your system. I use them (and like them) all the time to touchdown, but on a 5,000 footer may be a little sporty due to float issue that was mentioned.

 

[G3G4]

I understand the float issue, I actually wasn't flying. I always like to go to idle at 100 ft on a short runway. But non the less they should have gone to idle at 50 ft rad alt. I was just curious why they didn't when the gpws missed the 50 ft call out. Rad alt was working. Maybe we do have a rad alt problem

 

[paulsalem]

Not a Gulstream driver. But our audible altitude call outs are based on the CA side radio altimeter.

 

[doublepsych]

rad alt issue can be no bueno...

I understand the float issue, I actually wasn't flying. I always like to go to idle at 100 ft on a short runway. But non the less they should have gone to idle at 50 ft rad alt. I was just curious why they didn't when the gpws missed the 50 ft call out. Rad alt was working. Maybe we do have a rad alt problem

There have been some occurences of false 0 indications on the RA causing retard of TLs on approach and ensuing accident, (or maybe just a goat rope). ref: 737 turkish airline accident...

 

[gutshotdraw]

There have been some occurences of false 0 indications on the RA causing retard of TLs on approach and ensuing accident, (or maybe just a goat rope). ref: 737 turkish airline accident...

Now I have a third reason why I don't use it. Hadn't thought of it before but I suppose it could anytime you're in full landing configuration.

 

[Jetdriver69]

There is a reason why you keep your hands on the throttles and thumb near the AT disconnect when you are using the AT on any approach. As a rule, I disconnect the AT at the 50 ft call just in case and on any gusty approach prior to 500 AGL. Concerning a float with the AT, someone needs to work on their technique. The GV will float massively if you are light and you overflare, so stay ahead of the aircraft, flare at a lower altitude when light and you will do just fine.

 

[fokkerjet]

The system is only as good as its operator. Like the autopilot, never trust the automation when close to the ground, which means that one had is always on the yoke, and the other hand on the throttle (in our SOP) anytime the RA is active. Also, know what mode you’re in, how the automation will comply, and what you’re actually trying to do. Seen people command a descent, while on autopilot, click off the autopilot and level off. All the computers know, is that you want to descend, hence the power is reduced (or at idle), aircraft is level and the pilot is wondering why the throttle aren’t reacting. I always get rid of the flight director when maneuvering visually, say on a visual approach, with no lateral or vertical commands left in the guidance panel, other than speed. Works great, and haven’t been surprised.

 

[G3G4]

I understand tecnique and it has never scared me before, I was just curious if anyone had experienced this before and what they found the problem was. I know its a computer and they all have hickups somethimes but they happened both times in the same scenario. just trying to figure out what the problem might or could have been attributed to

 

[Gulfstream 200]

Auto-Retard is a marginally neat feature that often shares its name with the people who tend to rely on it.



Never saw one that worked well in anything but perfectly still air and dont know many people who use it.

 

[gutshotdraw]

Auto-Retard is a marginally neat feature that often shares its name with the people who tend to rely on it.



Never saw one that worked well in anything but perfectly still air and dont know many people who use it.

I wish fewer of my cohorts in this fleet used it...

 

[LJ45]

I've never flown with Autothrottles, of course I never had a problem hearing the 50 foot call and easying the power back. hehehe

 

[fokkerjet]

It’s not rocket science, at 50', throttles begin to go to idle. Whether you’re crossing the threshold at Vref -10, or Vref + 20, the system pulls the power off at 50’. Now it’s up to the PF to determine if 50’ is where you want the power pulled off. I’ve worked with various autothrottle systems, ie: Dassault, Fokker and Gulfstream, and they all require the PF to be in the loop at the approach/flare/roll out.

FYI, I've been using autothrottles since the late 90's, and as I stated earlier, you need to know what you've set up, in order to get the desired results.

 

[ProFracPilot]

The system is only as good as its operator. Like the autopilot, never trust the automation when close to the ground, which means that one had is always on the yoke, and the other hand on the throttle (in our SOP) anytime the RA is active. Also, know what mode you’re in, how the automation will comply, and what you’re actually trying to do. Seen people command a descent, while on autopilot, click off the autopilot and level off. All the computers know, is that you want to descend, hence the power is reduced (or at idle), aircraft is level and the pilot is wondering why the throttle aren’t reacting. I always get rid of the flight director when maneuvering visually, say on a visual approach, with no lateral or vertical commands left in the guidance panel, other than speed. Works great, and haven’t been surprised.

Or, the pilots fail to realize until they stall the airplane that they had pickled off the AT. I believe it was an American crew caused an A300 to stall at 16000' back in the 90's due to this oversight (then their screens all went into reset mode leaving them with nothing but standby instruments to recover, but that was an additional issue after the upset occurred). If you think about it, this could happen much easier than most of us think.

Imagine you're in a SPD commanded descent with the AP engaged on an arrival, trying to make a crossing restriction. The AT's aren't quite back at idle, and you need a little more descent rate to make a crossing restriction. So you disengage the AT's to make sure they stay at idle. Then the crew gets some kind of distraction (you pick it; VIP comes forward wanting to ask about ground trans, yada yada - whatever). I know, it is hard to imagine both crew are going to miss the various and obvious cues of the aircraft slowing as it captures the altitude for the crossing (such as how unbelievably quiet it gets as you're slowing through 150 kts). Next thing you know, you have stick shaker activation. Unlikely to happen? Sure, it's unlikely. But if any of us were to accidentally stall a jet aircraft, I'm convinced this would be the likely scenario where it would occur. We implemented this stall scenario into our sim training: Clean, AP on, AT's off, hands off until sticker activation. Not necessarily difficult to recover from in a training environment, but remember if it is going to happen it is because both crew lost SA. Real life reaction time would probably be delayed.

In aircraft with fully integrated flight management, we become as much system managers as we are pilots. One procedure I use to help me manage the automation is if the AT's are off, my right hand doesn't leave the power levers. I'm sure most of you do something similar.

My experience comes from the GIV. I don't fly a GV, but I can see where it would take some time (if ever) for me to trust the auto-retard feature.

Just my .02.

 

[semperfido]

Auto-Retard is a marginally neat feature that often shares its name with the people who tend to rely on it.



Never saw one that worked well in anything but perfectly still air and dont know many people who use it.

I wouldn't say I rely on it, but I do use it in the G550. It's whatever you get used to. I can understand why some folks just can't seem to adapt. Now shall I bring up the HUD and the Flare Que?

 

[gutshotdraw]

I wouldn't say I rely on it, but I do use it in the G550. It's whatever you get used to. I can understand why some folks just can't seem to adapt. Now shall I bring up the HUD and the Flare Que?

Adapt? Why should I "adapt" to something that could cause a problem for me (especially when I jump back into a IV)? Engineers frequently do because they can, not because they should.

And what's a HUD? Oh yeah, that useless thing I keep smashing my head into when I'm in the left seat.

 

[fokkerjet]

Adapt? Why should I "adapt" to something that could cause a problem for me (especially when I jump back into a IV)? Engineers frequently do because they can, not because they should.

And what's a HUD? Oh yeah, that useless thing I keep smashing my head into when I'm in the left seat.

Do you have "steam guages" in your GIV/GV, or did you adapt to glass?

 

[fokkerjet]

Now shall I bring up the HUD and the Flare Que?

:uzi:

 

[semperfido]

How about those suction toilets?

 

[ultrarunner]

Just some food for thought....

The 121 outfits have been flying with this type of automation for a VERY long time...auto-brakes, auto-spoilers, auto-land, fully integrated FMC's with auto-thrust, etc...

With that being said, their flight-crew SOP's have matured pretty well. And I can recall some specific COM procedures with respect to mixing and matching certain levels of automation in the interest of the highest level of safety, and so crews wouldn't make stuff up along the way.

I can dig some of that stuff up if folks are interested. But a post over at the majors board asking some questions might get you some pretty good info, as they've been flying this stuff longer than anyone.

 

[gutshotdraw]

Do you have "steam guages" in your GIV/GV, or did you adapt to glass?

I adapt to stuff that WORKS. I don't adapt to stuff that presents a potential safety issue. Auto-retard does IMO.

As for the suction toilets, they're great as long as you don't bump the button while you're sitting on them

 

[ultrarunner]

I adapt to stuff that WORKS. I don't adapt to stuff that presents a potential safety issue. Auto-retard does IMO....

Get in the sim and do some auto-lands.

Then try to do them with the AT's inop with CAT III C wx.

;-)

 

[gutshotdraw]

We don't have auto land. Still CAT 1 mins although EVS will get you to 100 AGL if you get the lights in the HUD.

 

[DC3Flyer]

Autothrottles

I adapt to stuff that WORKS. I don't adapt to stuff that presents a potential safety issue. Auto-retard does IMO.



If they're that bad then maybe you should have maintenance figure out what the problem is. All in all, the autothrottles work fairly well in our two airplanes. I'm a believer in flying the airplanes the way they were designed to be flown. I also fly a Falcon 2000 with no autothrottles so should I leave them off in the GV for consistency? So I don't forget what airplane I'm in....come on now.

 

[gutshotdraw]

Watch 8 or 10 people land 1500 feet long because of the auto-retard feature and get back to me. Not talking about auto-throttles. We're talking about 50' AGL auto-retard. Big difference.

 

[STAL6]

The EGPWS (call outs) and the A/T system both use the Rad Alt, but the EGPWS does not tell the A/T system to pull back to idle. If the a/c detects landing config than the RAD ALT is whats telling the A/Ts to pull back so I would suspect the RAD ALT system. You can test them both and make sure they go to 100 ft + - 5 ft ( they should be at -5 ft on the ground) also I think that the A/T system is using the RAD ALT that is selected on the pilots Display controller so you could try flying with #2 RAD ALT selected. If that does not work try Boxing the #2 A/T computer. Has for the 5000 ft runway I don't understand how that would effect it. I hope this helps.

 

[fokkerjet]

Watch 8 or 10 people land 1500 feet long because of the auto-retard feature and get back to me. Not talking about auto-throttles. We're talking about 50' AGL auto-retard. Big difference.

So you're crossing the threshold at Vref, and the throttles aren't starting towards idle at 50', causing "your pilots" to float 1500' down the runway? If they don't, write them up, and if they do,................well there's another problem, unrelated to autothrottles.

 

[gutshotdraw]

Let's just say, the auto-throttles work as advertised. I just don't like the commercial.


(Kind of like that dorky SWA commercial with the F/O and a guitar...)