Difficult to slow down

[Superpilotv2 2]

Hi guys,I´ve made several flight with the NGX since I got her yesterday and it´s perfect till now. But on every flight I made I had the problem that I found it very hard to slow down the plane. I´m somehow experienced with these kinds of FMC´s through flying the old ones in FS9 exesively but now i´ve come across something I don´t know any further:Every flight I made so far I had to make an go arround because every time I was way to high and too fast. I´m just back from an 700 MN hop to Juneau. I flew on FL360 and shortly before descent I resetted the MCP to 2500ft. The plane perfectly descended with 330 kts to arround 15.000ft when I took control over the speed management and changed the speed via the "Speed INTV" button to 300 kts while AP and LNAV and VNAV were enaged. That worked like a charm and we descended further. At arround 12.000ft the automatic kicked in and we slowed town to 240 kts. Well, we tried to slow down but in fact it didn´t work. Although the VS was near to zero the engines were at arround 50% N1 and also the help of the braking flaps nothing changed and the message "Unable to achieve VNAV Path" came up. I didn´t see that we were loosing speed at all I had set an target altitude of 4000 ft to the FAP but in fact I was arround 8000ft high when I overflew this point. If my memory treat me right this was alot easier to do in the old ones.So did I do something wrong or is that real world behaviour that the plane takes very long to slow down?

[Sekstifire 10]

The real world behavior is indeed that its a very slippery plane and it doesnt like to slow down while descending. You need to carefully manage your energy during descends. Also a descent at 330kts seems to be at an excessively high speed!

[FSX1234 0]

Hi, 330 does seem to be excessive speed for descent. When doing an ILS approach I start the descent when it gets to about 4.000 I drop the gear at this point my speed is 240knots, the gear causes drag so I begin to slow down. I then activate VOR LOC and leave my mcp at 3.000. My speed then drops and I extend the flaps. Once I get VOR LOC on the PFD I activate the APP and that's it speed begins to slow down to around 150 or whatever your VREF speed is. And then a perfect landing i always descend In VNAV unless need a quick descent.

[Paul Deemer 13]

Most common mistake here is people using 767, 747, MD-11 Cost index's. Use 40 or less. I use a cost index of 36 and this descends the aircraft on vnav at 280 knots. 330 knots is way too fast and why your having trouble slowing down. I flew into PAJN (Juneau) a few nights ago and it easy enough even with the bad weather.http://204.108.4.16/d-tpp/1113/01191LDAX8.PDFHow fast are you going on the LDA X approach? I am usually at 175 knots / Flaps 15 at 6100 and starting to descend.

[FSX1234 0]

I use cost index 25 which works well.

[Superpilotv2 2]

Uh, I wasn´t aware that the cost index has a that big role in this advanced simulation. Mine was at (no joke) 100, wich I have to confess is way too high but I´ve used that also in other planes. I´ll test it with 40 or less.Btw. is there any list out ther which tells me which airline uses which cost index?

[nikita 241]

it has been asked many times - and the only answer came from an airbus pilot -.-

[rocketfs 2]

Hi, 330 does seem to be excessive speed for descent. When doing an ILS approach I start the descent when it gets to about 4.000 I drop the gear at this point my speed is 240knots, the gear causes drag so I begin to slow down. I then activate VOR LOC and leave my mcp at 3.000. My speed then drops and I extend the flaps. Once I get VOR LOC on the PFD I activate the APP and that's it speed begins to slow down to around 150 or whatever your VREF speed is. And then a perfect landing i always descend In VNAV unless need a quick descent.

Euh,... lowering the gear at 4000' @ 240kts before llz capture as SOP?I suggest you dive into reading again...Bert Van Bulck

[gman1986 14]

I use a cost index of about 56 and I slow down fine. It's just a mixture of getting used to the plane, entering the correct descent forecast and using your own intuition. Make sure you give yourself enough time and just keep practicing.

[Paul Deemer 13]

Cost Index for Various Airlines

Air Baltic

• 28
• B757 CI: 50

Air Berlin

• 30

Air Canada

• B767s :100

Air France

• Short/medium haul flight : 35
• La Navette (France) : 250
• Longhaul : 45
• Delayed shorthaul : 250
• Delayed longhaul : 135

Air Malta

• B737 CI: 25

Air New Zealand

• B767: 45

Austrian

• 35

British AirwaysAirbus Fleet:

• A319/A320/A321
  • Climb at: Cost Index 0
  • Cruise at Cost Index 20

Boeing Fleet:

• Boeing 737-300/400 and 500 Series
  • Climb at: Cost Index 0
  • Cruise at Cost Index 28

• Boeing 747-400
  • Climb at: Cost Index 0
  • Cruise at Cost Index 90

Cost Index 0 (Sometimes used on East Coast USA to UK Flights and less often on UK to Singapore/Bangkok flights)

• Boeing 757-200 and Boeing 767-300
  • Climb at: Cost Index 0
  • Cruise at Cost Index 40

• Boeing 777-200
  • Climb at: Cost Index 0
  • Cruise at Cost Index 100

Cost Index 0 (Sometimes used on East Coast USA to UK Flights)British Midland

• 40

Cathay

• B744 CI:80

China Airlines

• 85 (Nur B747)

Condor

• Boeing 767-300ER: 30
• Boeing 757: 18

EasyJet

• Airbus A319 Cost Index: 12
• Airbus A320 Cost Index: 12
• Airbus A321 Cost Index: 23

EL AL

• 737's: 15-30
• 747's: 39(short/mid haul- Europe)757's: 20-40
• 767's: 30-45(30-40 for Europe, 40-45 long haul)
• 777's: 71(long haul, ex KLAX)

Emirates

• Airbus A330-200 Cost Index: 25

FlyGlobespan

• Boeing 737-700 Cost Index: 14
• Boeing 737-800 Cost Index: 13

FlyNiki

• 35

Hamburg International

• Airbus A319: 40
• Boeing 737-700: 30

KLM

• F70/100 Climb/Cruise : 30/15
• 737 Climb/Cruise : 30/15
• A330 Climb/Cruise/Descend : 60/150(300)/30
• MD11 Climb/Cruise/Descend : 50/100/20
• 777 Climb/Cruise/Descend : 50/100/20
• 747 Climb/Cruise/Descend : 150/300/50

Lufthansa

• Airbusse: 30
• Boeing 747-400: 70
• Airbus A300-600: 35
• Boeing 737-300: 25

Lufthansa Cargo

• 80

Luxair

• 50

Nordavia

• Boeing 737-500 CI-27

NordStar Airlines (??????)

• B737 NG: CI 30

Qantas

• B744 CI: 100
• Cost Index 40 for domestic flights
• Cost Index 20 for most International plans, however they may be planned up to CI250 to meet schedule/duty limits

Ryanair

• Boeing 737-800 Cost Index: 30

S7

• 30

SAS

• 45-50

Singapore Airlines

• B747/B777 CI:150

Skyexpress Russia

• B737CL
  • ?????????? = 28
  • ????????????? = 32

South African

• 50

Southwest Airlines

• 737-300/500 CI:28
• 737-700 CI:36

Swiss Airlines

• A32S:
  • FL290 and below: CI 10
  • above FL290: CI 20

• A330-200 and A340-300:
  • LRC: CI 30
  • M.082 Cruise: CI 30 for Climb/Descend and Cruise up to FL280, above M.082 manually edited
  • M.083 Cruise: CI 150 for Climb/Descend and Cruise up to FL290, above above M.083 manually edited

Thomson Airways

• Airbus A320 Cost Index: 13
• Airbus A321 Cost Index: 17
• Boeing 737-300 Cost Index: 10
• Boeing 737-800 Cost Index: 9
• Boeing 757-200 Cos Index: 10
• Boeing 767-300
• Long Haul Cost Index: 19
• Short Haul Cost Index: 11

Ukraine International Airlines

• cost index: 14
• B737 Classic: 19-20
• B737 NG: 28

United Airlines

• Flight with duration < 4 Hours:
  • A319 and A320 = Cost Index 27
  • B737-300 and B737-500 = Cost Index 35
  • B747-400 = Cost Index 90
  • B757-200 = Cost Index 80
  • B767-300 = Cost Index 65
  • B777-200 = Cost Index 85

• Flights with duration > 4 Hours:
  • A319 and A320 = Cost Index 22
  • B737-300 and B737-500 = Cost Index 30
  • B747-400 = Cost Index 85
  • B757-200 = Cost Index 75
  • B767-300 = Cost Index 60
  • B777-200 = Cost Index 80

Virgin Atlantic

• A340-300 CI = 30
• A340-600 CI = 40
• B747-400 CI = 73 - 93
• B747 :150

Westjet

• B737NG :20-25

[rictus 7]

This one used to get me into trouble on descents for a while until I had some practice (a good two months after getting the NGX). A good trick to help you get it right is to have a look at the STARs (Standard Approach) charts for your destination airfield and follow them through (and the SIDs - Standard Departures - for that matter!!!). The UK ones are all readily available for free in PDF from the AIP section of the NATS website. Look under 'aerodrome - specific' and you'll find them.Generally UK STARs enforce a maximum airspeed of 250kts. They provide a set of altitudes and a course to bring you gently down from the initial altitude, often around FL150 (15,000ft) to between 3000 and 2500ft and in a good position to turn and intercept the ILS. Remember your FMC knows all the STARs and they can be assigned to a flight using the DEP/ARR key on the FMC.Of course you have to plan your descent from your cruising altitude to the initial altitude on the STAR first. I found that took some practice. Fortunately I had some help from a real-world Easyjet pilot. He explained that you normally descend at roughly -1400 to -1800 fps, speed brake in the deployed position (it won't put the speed brakes on full during flight). You can then use the rule of thumb as follows:take your target altitude from your current altitude e.g. current: 30,000 minus target: 14,000 = 16,000. Lose the zeroes and times by three i.e. 16x3 = 48. That's the minimum distance in nautical miles that you want to be when you begin your descent. I recommend doing it by hand first rather than with the VNAV because then you'll get a proper feel for what you're doing. Real world pilots learn to do it 'by hand' first, then learn to let the aircraft do it, so that in the event of a problem (and I have had the LNAV in the NGX mess up on me) you can manage the flight yourself.The most important steps are done on the ground before you leave. If you want the LNAV to sort the descent for you, you've got to make sure you've done your INIT REF stuff first so the weights etc are programmed. Make sure you prog the whole route from beginning to end, then do your INIT REF and you'll see that the LEGS page is fully populated with waypoints, altitudes and speeds :)Finally, as to cost index, I fly for British Airways Virtual and all of their 737 flights are C.I. 28. In all cases, look at the excellent PMDG NGX manuals, look at the STARs and get comfortable with decoding them (doesn't take long) and most importantly remember - it's a simulator!! It doesn't matter if you mess something up, but you'll learn something by trying :)

[gman1986 14]

A few very good posts there guys

[Superpilotv2 2]

I use a cost index of about 56 and I slow down fine. It's just a mixture of getting used to the plane, entering the correct descent forecast and using your own intuition. Make sure you give yourself enough time and just keep practicing.

You´re right on this. It isn´t just hop in and push the throttles. I really have to practice again.

[kevinh 409]

Descending at 330 kts is not too fast. Long before you decelerate to approach speed you would decel to 240 below 10,000ft. So the speed above 10,000 ft has no bearing on the decel from 240 to approach speed. As for the easyJet pilot's advice, I've never been on any flight that descended with speedbrake extended the whole way. That certainly isn't usual. If you find yourself fast you can use speedbrake as much as you need to, maybe that is what they meant.Forget cost index, etc, the best advice is to think ahead. Stay ahead of the aircraft. VNAV should put you in a position where you can slow down to approach without drama. However as captain you need to progressively extend flap and reduce speed, beginning to do so in good time.Kevin Hall

[flyguy172 0]

cost index figures change all the time with airlines, usually in line with changes in fuel prices.if you put 20 or 200, you can always input your own figures for descent on the descent page.i put in a cost index of 100 at preflight, but I manually adjust the descent speed to 280, input descent forecast winds, and double check alt restrictions on the approach plate.and, there is always the speedbrake. i find pilots don't like using it because they think it's a black mark, but isn't it there to help slow down the plane? why not use it