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Difficult to slow her down during descent !

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One more note, above all good airmanship is the most influential component. You need to know your aircraft. :-)

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George Morris

 

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Rule of thumb for Descent profile management: 

 

A 3 deg path is roughly 1nm for 300ft 

 

300kts / 0.84    Distance to Touchdown x 3 - 5000ft  ( some people uses -4000ft, but I am a little more conservative)

250kts              Distance to Touchdown x 3 - 2000ft

Vref + 80          Distance to Touchdown x3 -1000ft

Vref +40 (at Flap speed)  Distance to Touchdown x3 

 

The airplane should be able to maintain Vref + 40 with Flap 5 idle thrust while descending on the G/S, although sometimes at heavy weight the speed will go up as the airplane pitches down for G/S intercept.  

 

So basically, if the CRZ ALT is FL350 at M.84, the TOD point should be (35000+5000)/300 = 133nm.

 

now look at the PROG page for the distance to touchdown as you descend. Let say you have now 100nm to go, you should be at 100x300 - 5000ft = 25000' so if you are still at 30000' you will need to either increase your descend speed from 300kts to 315kts or use speed brake, or both depends on how high above profile you are. 

 

I know there are lots of zeros, thats why people normally skipped the last two zeros of the altitude. So 100nm to go we need 100x3 - FL50 = FL250

 

using the same method at 15nm you should be at 4500' with Flap 5 or 3500' in clean configuration flying  at Vref + 80. And at 5nm 1500'.  

 

If the airport is not at sea level you will need to add the airport elevation to that. 

 

The above method using distance to touchdown x 3 is also very useful for people to cross check their approach profile when they are doing Visual or other non precision approach. 

 

There are many other ways of doing it, the above method is just one of them. ALT x 3 = Distance to touchdown also works. Remember it is just rule of thumb. As long as you arrives at the 5nm  @~1500ft AGL fully config with speed at Vref 30 + 5, you are doing the right thing. 

 

P.S The 777 is a slippery airplane comparing to the 747-400. Apart from a much cleaner airframe design, I reckon part of it is due to a much higher residual thrust at idle with the big engines, However slowing it down while descending is not as hard as a heavy weight A330 in my opinion. Its a much more speed stable airplane comparing to the airbus.

 

Hope it helps. 

 

Cheers

Mike

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Hi all,

 

Flies great but I have a problem slowing her down after passing T/D.

The 777 seems not to slow down enough and as a result I am at a much higher speed when reaching finals.

 

I know this a slippery plane. I use speed brakes, enter desired speeds into FMS but I just can't get it right.

 

Any others having the same problem?

 

 

Thanks,

Christos

 

Are the engines at or around idle until the first altitude constraint?


Regards

 

Howard

 

H D Isaacs

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Yes but I find it just enables me to have a more hands on approach when  coming in rather than letting plane do it. It's good to break away from the automation in long flights. 


James McAleese

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Probably he sets the throttles at 55% and after press the TOGA button, the throttle on joystick stay there, and engines don't come to idle. You must turn the throttles idle after engaging the A/P

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Jason Cardeira

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Has anyone tried the Ziggy4 arrival into KONT.  This is the most difficult approach I know of to slow down in any plane.

 

Sure did! My first attempt required a go around at the FAF landing west. Speed management is very important and it is up to the pilot to stay ahead of the airplane. The MD-11 shots the ZIGGY automatically slowing down at the HEC VOR before T/D, the 777 requires pilot intervention.


Dan Downs KCRP

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I have to admit that in all my attempts I had the exact opposite problem - I can't seem to keep up the speed above stall when I'm on a manual landing. 

 

It has been pretty frustrating few days. ;-)


Marko Milivojević

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Speed brakes and planning your way down. Today on my flight I descended a little early with V/S to get unther the track the FMC had me planned on untill my first altitude speed restriction. From that point on I was able to VNAV my way around with the use of speedbrakes when I needed to slow down. On finals the gear adds a lot of drag to slow the rest down.


Best regards,

 

 

Stefan van Hierden

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I have to admit that in all my attempts I had the exact opposite problem - I can't seem to keep up the speed above stall when I'm on a manual landing. 

 

It has been pretty frustrating few days. ;-)

lol Im too fast on descent and to slow on approach and my FPM on landing is a real smack down, getting better though.


 

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Has anyone tried the Ziggy4 arrival into KONT.  This is the most difficult approach I know of to slow down in any plane.

Even though the ZIGGY arrival does intersect the ILS at PETIS, it's pretty much impossible to do due to terrain and speed. Normally ATC will vector you South, then East, then North, and finally back West to the ILS. I've heard this referred to as "toilet bowl sequencing" for obvious reasons  :lol:

 

The ZIGGY into ONT, and the KAYOH into SNA are the 2 most difficult arrivals to control in SoCal. Speed control is absolutely critical on both.


Steve Caffey

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The FCTM calls for 3nm per 1000ft of altitude loss when descending at ECON speed. It also has a chart that gives achievable descent rates below 20,000ft when descending at .84/310, 250 and then Min Maneuver. Slowing from 310 to 250 takes 1nm per 10kts clean and level. It takes 4nm to slow from 250 to flaps up maneuvering speeds at average gross weights. 

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What's your CI. Note that a high value will calculate late TOD (the A/C will stay in cruise as long as possible). Having tailwind is not going to help your descent either.


 

Regards,

Martin Martinov / VATSIM 1207931

 

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Even though the ZIGGY arrival does intersect the ILS at PETIS, it's pretty much impossible to do due to terrain and speed. Normally ATC will vector you South, then East, then North, and finally back West to the ILS. I've heard this referred to as "toilet bowl sequencing" for obvious reasons  :lol:

 

The ZIGGY into ONT, and the KAYOH into SNA are the 2 most difficult arrivals to control in SoCal. Speed control is absolutely critical on both.

 

Flew the freighter route PANC - KONT today with the Ziggy4 into 26L.  It was on Vatsim with ATC online.  I had planned to cross MAJEC at 10,500 but the controller gave me 15,000 at MAJEC.  Thankfully he later decended me to 8000 cancelling the restriction and I decended MAJEC around 11,000ft (by the way I got this number by looking at the track on Flightaware for the UPS MD-11 flight earlier today.  At the long/lat of MAJEC they were at 10,500.)  Anyway, after that it was descend to PETIS at 4200 to intercept.  I had to have the speedbrakes out then, gear down and flaps 20 to slow down but managed to get to 200 knots for intercepts and made my first full autoland today in the T7 thanks to very low vis at KONT this morning.  All in all not too bad for this challenging approach.


Mark W   CYYZ      

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I just plug in all the descent winds data I can get my hands on. Wind at destination at FL320 FL240, FL180, and 7000ft or whatever.

 

have hardly even needed to use speedbrake. 180kts or less at glideslope intercept, gear down, wind it back to 160kts and get the flaps out on schedule. Vref+5 selected before outer marker, Landing flap and speed established before passing 1000ft on descent.

 

Capturing glideslope from Below is easy... haven't been slam-dunked into an intercept glideslope from above on vatsim yet, that might be a bit more hectic.

 

I might need to practice some of that action for Cross the Pond next month. I'm told they do intercept-from-above slope at EHAM sometimes.


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