FLCH Trap?

[Guest Q_flyer]

As others have widely covered, the 777 is acting correctly;  your setting 0 altitude in the MCP is the factor that would could the FL CH mode to do what it is supposed to do (descend at a selected speed, with idle thrust, by adjusting aircraft pitch), but in your case down to zero altitude which obviously  = crash.

 

If for example you had selected 3000 in the MCP Alt window, the FL CH mode would have gone down to 3000, then the A/T would have taken over, using engine thrust to maintain the selected speed, once level.

Good luck! Welcome to the burnt engine club, you are likely to roast a few!

Sent from my Mobile thing

 

If you always use the Autothrottle in the Maddog, and always remember to set T/O (or even better Flex T/O) on the TRP, you'll never roast an engine! :smile:

[WR269 367]

 

If you always use the Autothrottle in the Maddog, and always remember to set T/O (or even better Flex T/O) on the TRP, you'll never roast an engine! :smile:

Where's the fun in that? May as well watch a Just Planes video. Have a go, learn how to manually set EPR, manually control thrust and fly the beast.

 

Best felong of satisfaction when it all comes together.

 

The Maddog is still quite a machine.

 

Sent from my Mobile thing

 

 

[xkoote 57]

Hello guys,

 

yes, IAS/MACH HOLD is identical to the FL CH in Boeings. In descent, the A/T will clamp (clutches disengaged, or similar to armed in Boeings I guess). If you disengage the autopilot and level off the speed will bleed off with the thrust in idle.

 

It was very amusing in reading of the burned engine club ;-). As I drive the Dog for a living I'm still not a member. But I do remember all my friends chatting me up and asking why in hell they keep getting engine fires.

 

To go off topic for a sec, I feel so blessed to be able to fly the Mad Dog. She's truly a wonderful machine, mixing old school and modern technology. And even more blessed to have the chance to fly here in the Caribbean. Where 95% of all descents are continuous, and you are free to make your flight as enjoyable as you can. Visual approaches, tight base turns, getting to know your plane. Can't imagine doing it in any other type. The Dog. Now - I think - truly, the last of the breed.

 

My apologies, back on topic (No beer emoji??? Come on!)

 

Xander  :wink2:

[G550flyer 1,074]

 

 

Should FLCH never be used during approaches?

One way to visualize this is to think of the glide paths that approaches have. FLCH will give you the maximum descent rate achievable for a given airspeed and configuration. This will very well exceed any standard 3 degree glide path. Pretty much impossible to follow a glide path in FLCH. Even on a visual with out visual guidance, I still fly a 3 degree path. The only time I use FLCH on approach is when the controller keeps me high and I'm above the glide path. I select FLCH but I also arm the approach button or VNAV depending on the type approach flown. The real world jets I fly will switch to speed mode as the glide path/slope is being captured.

 

The funny thing in the Gulfstream is that we actually set 0 in the altitude window depending on how we choose to fly a GPS approach. If i fly it LNAV/VNAV and choose to use a DDA, I add 50ft to MDA. I select 0 in the window, ride the VNAV down to DDA and either land or go around. I could also fly that same approach in LNAV and simply put MDA in the window and allow the jet to level off. In either situation, the PNF gets very busy on the go as he has to get the flaps to go around setting, gear on my command, set missed app alt, set and lock 180kts, set/confirm my lateral and vertical modes for the missed app, and back to the flaps for retraction on my command. Atleast on the G550, I can select the approach button for/ARM the LNAV/VNAV approach and then dial in missed app alt.

[Fabo 213]

 

 

It was very amusing in reading of the burned engine club ;-). As I drive the Dog for a living I'm still not a member. But I do remember all my friends chatting me up and asking why in hell they keep getting engine fires.

 

Truth be told, I never burned one myself... except on startup once when I forgot I was not in a 737CL and let the fuel in early (late night). But I managed to stop the needle before going too much over max.

 

Never burned one on takeoff.

[BeechPapa 32]

One way to visualize this is to think of the glide paths that approaches have. FLCH will give you the maximum descent rate achievable for a given airspeed and configuration. This will very well exceed any standard 3 degree glide path. Pretty much impossible to follow a glide path in FLCH. Even on a visual with out visual guidance, I still fly a 3 degree path. The only time I use FLCH on approach is when the controller keeps me high and I'm above the glide path. I select FLCH but I also arm the approach button or VNAV depending on the type approach flown. The real world jets I fly will switch to speed mode as the glide path/slope is being captured.

Thanks for the input, I'm very happy to see pilots commenting on this thread and sharing their knowledge with simmers. I've looked alot for a Gulfstream in FSX, but there aren't any good ones available. The G550 must be a sweet ride.

 

One thing I should clear up, because I've heard it mentioned a few times, is the fact I couldn't have been on a 3 degree GS. Well... I wasn't! I was way above it. This chart from http://flyingprofessors.net/what-happened-to-asiana-airlines-flight-214-2/ explains the situation perfectly: (black line is a normal approach, red line was Asiana)

 

 

I’m not a professional pilot, and can’t comment on anything with any RL context, but the behavior of the sim was deceptive in that it seemed to me I was getting back on GS. I was staring right at the speed tape too, watching the flap indicators as I dropped it notch by notch, and waiting for the max speed indicator for the given flap angles to drop as well. In retrospect, I was in the process of stalling the plane but in my mind I was decreasing lift (and doing a damn good job of it!) so I could get back on GS and simultaneously drop speed. At flaps 30, I had done myself in completely, but at the time it felt like relief since I was finally on GS at VREF. When I began to prepare for manual control, and passed the DH (600ft) at 137kt, then passed 500ft at 128kt, 400ft at 118kt – those moments were literally seconds and I got that uncanny feeling of “something’s wrong” when I realized I was at 0 degree pitch but still losing altitude. And the typical drone of the engines with full flaps were missing, things were too quiet. But all those indicators of a bad situation went by extremely quickly. With the engines requiring 5 seconds just to spool up, the only way I can imagine avoiding this situation is to see it coming ahead of time. I’m a lone simmer (with obviously limited experience) sitting in front of a computer, so can’t really explain the actions or perceptions of an entire senior crew of captains in the cockpit. They should know the airplane inside and out, and be aware of every aspect of the AP system. But things came apart really quickly for me, it was the kind of situation where once I realized what was happening it was already too late. The situation went from too high/too fast to acceptable to horribly wrong in the space of 200 or 300 ft. I'm not making any excuses for my failure to pilot this situation, there's no excuse for that, just trying to explain how everything fell apart so quickly.

[FLEX1978 373]

Hey Ethan,

 

It must always be about meeting stable approach criteria. I will post a link below, one extremely important factor that is mentioned and should be in your mind is 'engines spooled & airspeed stable within the allowed Vref deviation tolerance at the minimum of 1000 IMC or 500 VMC

 

http://www.skybrary.aero/index.php/Stabilised_Approach

 

It's all good fun, and no one is getting hurt through the learning curve, 10 - 15 years ago I couldn't imagine having to worry about stuff like this on a desktop sim, I can remember when I used to put the default FS98 737 in a vertical dive, engage reverse thrust and it would hover at 0 IAS

 

Btw, after reading the link I am pretty sure you can drop to a maximum of Vref -5 at least with some airlines!

[Driverab330 74]

After reading your post, just a few points here may be you can have a look at before you attempt to fly the same approach next time.

 

1) never rush for an approach, if you don't think you can be fully configured and speed reducing towards Vref + 5kts by 1500ft AGL, go around and come back again. Most of the landing accidents ( runway overruns or landed short from thenthreshold ) happened recently due to unstable approach. So if you don't think you can make it, press TOGA.

 

2) never use FLCH for approach and never set MCP to zero. Boeing FCTM recommends setting MCP to MDA in the worse case for Non precision approach or 1000' + airport elev for ILS when trying to capture from above the G/S. you may use the VNAV scale for guidance as well if you are high, they are very accurate after passing the IAF in most cases provided that the FM is programmed correctly.

 

For Non precision approaches, when established on final and 300ft below the miss approach altitude you can set the Miss approach alt in the MCP window.

 

Use V/s mode whenever you try to capture from above the G/S. set -1500ft/min initiately, within 180kts flap 15 would do most of the time. Because A/T will remain in Speed mode.

 

3) monitor your altitude against the track miles to run using the prog page in the FM or the ILS/ VOR DME distance if they are co located or very close the runway threshold , ie 5 nm you need to be 1500ft, 3nm around 900ft etc etc. the Rate of descend should be half of your Ground speed.

 

4) think ahead as well how you gonna fly the approach. The airplane flies very fast and take a while to slow down. So anticipate the capture of the G/S, try to descend no faster than 180kts flap 5 or 15 to begin with ( at heavy weight the speed will increase with flap 5 while descend on the G/S with idle thrust ). Once you become more familiar with the airplane you can be more aggressive with the profile.

 

Hope it helps. Enjoy the 777. Remember it has a lot of inertia, anticipate it and you will be able to fly it very well.

[BeechPapa 32]

Hey Ethan,

 

It is always about meeting stable approach criteria. I will post a link below however an extremely important factor that is mentioned and should be in your mind is 'engines spooled & airspeed stable within the allowed Vref deviation tolerance at the minimum of 1000 IMC or 500 VMC

 

http://www.skybrary.aero/index.php/Stabilised_Approach

 

It's all good fun, and no one is getting hurt through the learning curve, 10 - 15 years ago I couldn't imagine having to worry about stuff like this on a desktop sim, I can remember when I used to put the default FS98 737 in a vertical dive, engage reverse thrust and it would hover at 0 IAS

 

Btw, after reading the link I am pretty sure you can drop to a maximum of Vref -5 at least with some airlines!

Thanks Rob,

 

I appreciate the knowledge as well as the encouraging words. I always have great fun with the 777, but after the crash I remember having 3 distinct thoughts: 1) holy $&*! 2) what if there were actual people back there? and 3) thank God this is only a sim. It's quite a learning curve, which makes me all the more respectful of real world pilots who have no quit button.

 

After following your link, I can definitively say I was not on a stabilized approach. This will come in handy, and approach phase is an area I need to work on. I'm rushing into things. Thanks for the info.