Some questions about airline piloting...

[Noel 4,499]

 

This is a duplicate post from Hanger Chat in case you don't go there.

1. What is a typical taxi speed for commercial airliners, when the taxiway is free and clear of anything else to be concerned about?
2. What is the range of miles out from destination where the crew is directed to land via a certain STAR/approach?  IOW, how early in a flight is crew aware of what they will need to do for approach and landing?
3. Is it a rule/custom worldwide, or US, etc, to turn ON landing lights upon entering the runway, and OFF at 10K feet, and/or adjusted according to the highest elevation in the departure/arrival/alternate, and back to ON accordingly on descent and approach? 
   1. If the above is true more or less, when crew is told to Hold Short at Rwy X for departure, do they turn LL on then, while holding short?
4. What is the maximum descent rate for the bigger airliners?
5. What determines the highest altitude in the Flight Plan?  Is it the general philosophy to fly as high as possible/allowable for that aircraft, so as to allow the most altitude for safety reasons, for example in the event of a mechanical failure to have more time/distance to try to make a safe landing, etc?
6. In airliners in MSFS in the FMC there might be an LSK for inputting the Cost.  What is this really saying/asking?  Does the value input impact throttle mapping or what have you?

Thanks in advance!

[MrBitstFlyer 3,873]

1 hour ago, Noel said:

What is the range of miles out from destination where the crew is directed to land via a certain STAR/approach?  IOW, how early in a flight is crew aware of what they will need to do for approach and landing?

In the UK pilots from the south get their STAR allocated on first contact with London ATC.  From the south this will be over northern France - flights into Gatwick especially don't get a lot of warning!

[iwebber 207]

Hi Noel,

The answers to all your questions (as in most in the professional world) is "it depends...".

However, to generalise (while trying not to upset the purests and the pedants)...

1) 30kts

2) STARs are usually filed in the flight plan so you have a good idea as to what you're going to get but every airport is different. Usually before top of descent you'll get a clearance (or at least a hint/tip) for the STAR. In some places they're nice enough to give you the runway as well but not everywhere (I'm looking at you, Frankfurt).

3) I'm unaware of any hard and fast rules about lights but I've not met many airliner pilots who don't want to be seen. Turning the lights on below 10000(ish) is common for airliners whose lights don't extend into the airflow; and turning them on when on a runway (or on receipt of take off clearance sometimes) is generally what happens. Same with the other lights, if you need them, use them, if you don't, switch them off.

4) There's no limit in my company although we're limited to -10 pitch. We also have a limit of 3000fpm within 3000ft of the MSA but that's company specific and not a rule. I think Air France 447 achieved -11000fpm but I'm not sure that's one to copy.

5) Weight and weather, the general philosophy is to cost as little as possible (some worry about making schedule too).

6) This is a massive subject but the cost index basically tells the FMC how to balance flight time and fuel burn. Max cost index = quickest flight time, lowest cost index = minimum fuel. Modern FMCs are very clever and will take winds, temps, weights and trip length into account to give you the best speeds/alts to fly at to achieve this.

Hope this helps,
Ian

[qqwertz 781]

Hi Noel,

4. As far as I know, this is merely limited by structural integrity, i.e., you should not descend so quickly that you surpass VMO. For instance, if the airplane loses pressurization, pilots will generally descend to a safe altitude (around 10000') as quickly as possible. Under normal operations, airplanes will descend at a rate that guarantees passenger comfort.

5. That's complicated. Generally, the higher the better since the air gets thinner and there is less parasitic drag (drag that is not associated with generating lift). You can save a lot of fuel by being up high. However, you first spend a lot of fuel for climbing that high. On shorter flights, cruise altitude is therefore determined by a compromise between the costs of climbing and of flying low. Typically, you still climb as high as possible, but only at the optimal climb rate, not quicker.

On longer flights, the maximum altitude is determined by the weight of the airplane. Thinner air also means less lift, which you need to counter the weight force. Hence, airplanes can climb higher when they are light. On very long flights, jets generally do step climbing. Initially, they climb to a lower altitude, say 34000'. As the flight progresses, the airplane burns fuel and gets lighter, hence it can fly higher. For instance, to 36000' after 2 hours and to 38000' after 4 hours of flight. It is called step climb because they still have to fly at a flight level. Over land, the steps tend to be 2000' since (in North America and parts of Europe) even flight levels are assigned to airplanes that fly west and odd flight levels to eastwards flights, but over the Atlantic the steps can be 1000'.

Another factor for determining the optimal cruise altitude is wind. Its speed generally varies with altitude, so that it may be better to fly at low altitudes if you face a strong headwind higher up. This plays a huge role for transatlantic flights in particular because of the jet stream, a strong easterly wind at mid-range latitudes that changes all the time. NAT tracks are determined twice daily based on the jet stream. Eastbound tracks tend to be at lower latitudes to pick up the jet stream and get a strong tailwind. Westbound track are more towards the North to avoid the jet stream.

My wife recently flew from Austin to Toronto during a cold snap in the Eastern US and I followed her flight on Flightaware. Her plane initially climbed to 34000', then descended to 30000' because the jet stream was very far South and pointed in a SE direction. After an hour, the climbed back to 34000'.

6. I only know that the cost factor numbers are different for Boeing and Airbus jets.

[BerndB 349]

9 hours ago, Noel said:

This is a duplicate post from Hanger Chat in case you don't go there.

1. What is a typical taxi speed for commercial airliners, when the taxiway is free and clear of anything else to be concerned about?
2. What is the range of miles out from destination where the crew is directed to land via a certain STAR/approach?  IOW, how early in a flight is crew aware of what they will need to do for approach and landing?
3. Is it a rule/custom worldwide, or US, etc, to turn ON landing lights upon entering the runway, and OFF at 10K feet, and/or adjusted according to the highest elevation in the departure/arrival/alternate, and back to ON accordingly on descent and approach? 
   1. If the above is true more or less, when crew is told to Hold Short at Rwy X for departure, do they turn LL on then, while holding short?
4. What is the maximum descent rate for the bigger airliners?
5. What determines the highest altitude in the Flight Plan?  Is it the general philosophy to fly as high as possible/allowable for that aircraft, so as to allow the most altitude for safety reasons, for example in the event of a mechanical failure to have more time/distance to try to make a safe landing, etc?
6. In airliners in MSFS in the FMC there might be an LSK for inputting the Cost.  What is this really saying/asking?  Does the value input impact throttle mapping or what have you?

Thanks in advance!

Noel, as my pre-answerers already mentioned, those "rules" are depend on three basic things. The FCOM procedures for the specific Airliner, the company rules and the rules in the specific region where you fly.

I will give you some examples which are valid for an Airbus A320:

1. The maximum allowed taxi speed is 30 knots on straight tw. The max. speed at 90 degree turns is 10 knots. This is instructed by Airbus for their aircraft limit. Usually you taxi with a speed somewhere between 15 and 28 knots. Because, if you get over the max allowed, many companies will give a QR (Quakity-fail-report) to the Captain.

2. Based on the runway in use and on the weather at destination the flightcrew can estimate the STAR which will be given for a certain RW. It´s already filed in the FP by operation but while in flight the conditions at destination can change. In general you even could ask atc for a specific approach and if possible they allow. Keep in mind, the Captain of the Aircraft is the one and only person responsible for the aircraft, if he can´t cope with an instruction. 

3. One major reason for landing lights is to prevent bird strikes. This is why landing lights are mandatory usually between 0 - 10.000 feet. (Above 10k feet there usually no birds anymore). For the A320 the FCOM-procedure is turn on LL when enter the RW for take-off and switch off LL above 10k feet (10k feet action). The same vice versa when decent below 10k feet. If the Crew is told to hold short at RW Checkpoint, maybe waiting for a incoming aircraft, it´s usual to turn of the lights (Landing and Taxilights) When you are cleared for take-off or for line-up, you switch on Strobes, taxilight and Landinglight for entering the RW. There are some pilots who are not strictly follow these procedure, but if you get a bird strike, and they figure out you´re LL wasn´t switched on below 10kfeet, you will get a lot of trouble at least. In some compmanies you will pay a high penalty in case. Think about the costs of repair...

4. I think it´s 80 meters per second, because this is the maximum speed a mass is falling in the earthcores direction, based in gravitational rules. But this would overstress the airframe and wouldn´t be comfortable for the PAX. In general it depends on the max. allowed g-forces for an airframe. Usually an airliner decent´s between 1000 and 2500 feet per minute on an usual decentpath in managed mode. You can make a expedite decent aswell, which can have decentrates above 2000 ft up to 4.500 feet p. minute, but this can have very uncomfortable feelings for PAX and Crew because of the pressure change. 

5. Usually as higher an Jet-aircraft can get, as more economic the consumption of fuel will be. But this is much more relevant for long range flying. And you should also have mind, that you and your crew get a lot more interstellar rays as higher you get, which increase the cancerrisk for pilots dramatically. Many l pilots restrict themselves not to go higher than 35.000 feet. But there is also an safety reason for not getting too high. The A320 maximum ALT is about 39.000 feet. But if you would fly at that ALT the range between overspeed and stallspeed is just 15 - 25 knots. Why would you risk to get into these redzones if you get windchanges or even turbulence at high altitudes?!. On the other hand the economic highest ALT depends on the distance of the leg. I. ex. it wouldn´t make sense to try to get a full loaded A320 to a CruiseALT of 37.000 feet on a trip from Hamburg to Düsseldorf. Those short´s would usually end at Cruiselevel of 280, may be 300. A Trip from Hamburg to Munich you will usually Cruise at 320 - 350. At least you´r cruise ALT should be choosen that you can determine a minimum time of 15 to 20 minutes at that Cruiselevel. Anything else wouldn´t make sense.  

6. During a flight the cost mainly comes from two different things: the hourly crew cost and the fuel cost, both depends on time. The cost index synthesizes both costs in order to minimize the cost of a specific flight by giving priority to the fuel consumption or the flight time. This allows to calculate speeds and optimum altitudes. In a nutshell the higher the CI is,  CI = Crew cost per time / Cost per fuel qty.

The CI is usually computed and ruled by a companies operaton and the actual one is been given to the flightscrews by OPS.

 

[Noel 4,499]

Thanks everybody that is great!  MSFS ATC waits until the last minute to clear your approach frequently and I wondered how realistic that is.  Of course it can happen as you mention but is perhaps less common than MSFS thinks it ought to be!  I appreciate the fact MSFS lets you request runways that are sometimes very much not aligned so often you can get what the local METAR from 3rd parties are showing so it can work to use MSFS ATC and get away with it.  I've had several flights lately where ATC did not direct me into the runway w/ a headwind and was able to request a better runway.  Descent is initiated reasonably far out thankfully.   Yesterday I flew Lima to Cuzco and was shocked at how spot on all the descent calls were all the way into this challenging mountainous approach it was remarkable!    Taxiing I thought had to be kept around 15 knots but that apparently isn't the case for straight unobstructed taxiways.  I also typically put 100 in the Cost Index field but assumed it must modulate variables as you describe but never did anything to see if planes like PMDG or AS CRJ actually model this as far as fuel management or what have you goes.  I've modulated cruise altitude because of winds because it seemed appropriate and sounds like it happens in the RW for efficiency reasons etc.

Thanks again!

[BerndB 349]

5 hours ago, Noel said:

Thanks everybody that is great!  Descent is initiated reasonably far out thankfully.   Yesterday I flew Lima to Cuzco and was shocked at how spot on all the descent calls were all the way into this challenging mountainous approach it was remarkable!   

You´re welcome Noel, and just an additional tip from realworld flying: I´am honestly not sure how it´s shown in a Boing or CRJ, but in operating an Airbus A320, there is a very important point in the FMGS flightplan, that´s the TOD top of decent computed by the aircrafts FMGS computer. This WP would be the right point for the start of the descent, based on the aicraftparameters and the conditions at the destination. Most of "bad" approaches are happen on the fact, that you are too high and too fast at the final decent point (the point where the final decent for landing starts). To prevent from this to happen it is common procedure in airliner flying, to set an altitude and speed constraint at the last WP before the FP in your FMGS. This would bring up the TOD a little bit more upfront and if your decent was as computed, you will reach the FP at the correct altitude and speed. The constraints to set here are the Final approach altitude of the actual RW and the VAPP (velocity at approach) of the actual ac condition, which is shown on the Approachpage of the FMGS. Don´t hesitate to demand the allowance for decent from ATC, once you´ve reached the TOD. That´s what´s done in realworld aswell. Keep in mind, that the Pilot is responsible for being able to operate the aircraft conform to the procedures, not ATC. And of course, if an instruction by ATC given to you would end in a crash into the mountains, it´s the Pilots responsibility ONLY, to prevent it and ask for better instructions.  

They will not write on a Pilot´s gravestone "He lies here because he just followed the ATC instructions" 

Edited April 19, 2022 by BerndB

[Noel 4,499]

1 hour ago, BerndB said:

Most of "bad" approaches are happen on the fact, that you are too high and too fast at the final decent point (the point where the final decent for landing starts)

As a non RW pilot I can appreciate that--it's the source my 'bad' approaches in flight sims no surprises there.  In the case of FSX/P3D this was from following ATC which seems to wait too long to start the descent.  In MSFS I find the descent seems very early by comparison, but then as you get closer to final descent ATC sometimes doesn't continue to direct me down, and other times directs me to 2000' AGL 40m out!  What is considered 'final descent'?   I hope they continue to develop ATC it does have promise in certain areas.  

[Noel 4,499]

1 hour ago, BerndB said:

They will not write on a Pilot´s gravestone "He lies here because he just followed the ATC instructions"

I was stunned at how spot on ATC called the approach into Cuzco.  Each step of the way down they were right on target it was amazing!  

I have set speed constraints for just the reason you mention when in the PMDG birds in P3D.  I obviously am not a RW pilot and when to the infamous T&E Flight School but some things are self-evident enough.  Thanks again!

[SAS443 1,723]

5 minutes ago, Noel said:

What is considered 'final descent'?

Around here (EASA country) it is when you leave platform altitude  (from a level segment between the IF and FAP on a precision approach) and travel down the glideslope.

Or anytime you are outbound from the FAF/FAP more or less...