Archived

This topic is now archived and is closed to further replies.

ahinterl

MD-11: Please enlighten me on speed bugs

Recommended Posts

Another one where I'm pretty puzzled are the speed bugs. I now like to know whether there is a simple method how to get things right.Looking at the speed tape during takeoff and approach/landing somehow gives me a bad feeling when I see many the bugs 'at the same time' without knowing what they mean in more detail.Being used to use the bugs as the maneuver speeds for a certain flaps setting (and the typical Boeing/Airbus flaps scheduling scheme), I for instance wonder about that when I take off with e.g. flaps 28 I find the -F35 bug at a speed well up on the speed scale.So, it seems my usual approach to use the next flaps bug I find on the scale as the point when to retract to the next lower flaps setting during acceleration is wrong. Same for approach. Somehow I have bugs like -F50 above the speed I currently fly during deceleration on approach often.Can someone please shine a light for me on those bugs and how to use them correctly? I want to be able to tell what the bugs are and what they mean if someone shows me any speed tape situation and requires me to analyze what's going on in that exact situation and what the pilot's duties are.Furthermore, is it normal that after takeoff with a given dial-a-flaps setting the flaps are moved to up at the -FR bug without having an "intermediate" setting in between? From 22 to 0 looks like a big amount of flaps to me, Boeings have even several settings between 10 and 0...Andreas

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

The quick answer is this is not a Boeing. The speed tape bugs are not used to schedule flaps going in or out, and flap retraction is indeed one step followed by slat retraction.The answer for approaches depends on the environment, but in general the flap status is tied to the FMS calculated speed using ATS. Therefore, lower the flaps where appropriate in the pattern. For example, I will put the slats out on downwind or when I want to start slowing from 245, then add 15 flaps on base or before final vector to final which will slow things to under 200. The gear and flaps 28 come out on intercept for final then flaps 35 for landing when on glideslop. I don't have any real experience in the bird, and I am still finding ways of making the approach smoother but so far this method has been working okay. Note that this method is very different from the 737/747 in the way flaps and speed interact.Hope this helps.

Share this post


Link to post
Share on other sites

But from the naming "flap extension" and "flap retraction" of the bugs I derive they have something to do with extension and retraction speeds. The question is only how they do that.I can imagine "FR" and "SR" are indeed the points where a retraction should take place since according to the manual these bugs are amber when speed is either below or more than 10 kts above them and they're green when speed is at these bugs.What I cannot properly decyper is the "FE" and "SE" bugs because they're amber when speed is above a certain limit (probably the flaps extension limit speed for a given flap setting) only and green otherwise, so they'd stay green whenever below the limit speed and thus don't give such a visual response in terms of color change as the "FR"/"SR" bugs do.Nevertheless I think the "FE"/"SE" bugs must have a dedicated meaning in terms of what to do when these bugs approach the current speed pointer...Andreas

Share this post


Link to post
Share on other sites

Hi!From the Russian terminology SE would mean Slat Extrraction and FE would be Flap Extraction.But, I might be wrong!Ricardo

Share this post


Link to post
Share on other sites

Here is the information, Next time please just break out the manual. It contains all the information you need!FR Bug (Flap Retract, source: FMC)- The FR bug is normally green and appears only when flaps are extended. The FR bug will be removed when flaps are retracted. The FR bug turns amber if: Current airspeed is below FR speed, or Flaps are extended at FR speed + 10 knots, or Flap display below speed tape is amber for any reason.SR Bug (Slat Retract, source: FMC)- The SR bug is normally green and appears only when slats are extended. The SR bug will be removed when slats are retracted. The SR bug turns amber if: Current airspeed is below SR speed, or Slats are extended at SR speed +10 knots, or Slat display below speed tape is amber for any reason.GR Bug (Gear Retract, source: EIS)- The GR bug appears only when landing gear is down. The GR bug is green when the current airspeed is below the gear extend limits. The GR bug turns amber if gear is extended above 230 knots or Mach 0.7.SE Bug (Slats Extend, source: EIS)- The SE bug is normally green and appears only when slats are retracted and speed is more than 220 knots with Mach displayed (or more than 255 knots with Mach not displayed). The SE bug turns amber when speed is more than 280 knots (Mach 0.55).FE Bug (Flaps Extend, source: EIS)- The FE bugs (-F15,-F28,-F35,-F50) are normally green and appear only when speed is less than 255 knots and altitude is less than 18,000 feet. The bugs also appear if slats or flaps are extended and more than 60 seconds have elapsed since TAKEOFF mode was exited.The FE Bugs turn amber as follows:The F15 bug turns amber when speed is more than 255 knots.The F28 bug turns amber when speed is more than 210 knots.The F35 bug turns amber when speed is more than 190 knots.The F50 bug turns amber when speed is more than 175 knots.GE Bug (Gear Extend, source: EIS)- The GE bug is always displayed. If gear is retracted, then GE is 260 knots (0.7 Mach). If gear is extended, GE is 300 knots (0.7 Mach). GE turns amber when airspeed is above gear extend speed.

Share this post


Link to post
Share on other sites

Well, that's all correct, and I've read the manual several times, but one thing is still unclear to me:Whereas I can tell what the "retract" (FR/SR/GR) bugs mean (i.e. retract things when the bug wanders through the speed pointer, coming from above), what is required for the "extend" bugs, e.g. if "-FE28" is at the speed pointer position? I can imagine that GE indicates the maximum speed the gear can be extended, but have no clue what the flaps/slats extension bugs mean (maneuver speeds)? Looks like the extension speeds include a visual cue to the maximum extension speed for a given flaps/slats setting by coloring the bug amber if maximum speed is exceeded.Andreas

Share this post


Link to post
Share on other sites
Looks like the extension speeds include a visual cue to the maximum extension speed for a given flaps/slats setting by coloring the bug amber if maximum speed is exceeded.Andreas
That is how I understand them.For any given flap setting, the maximum and minimum speeds are indicated on the airspeed indicator by the red and yellow bands to the left. Climbing out, the bugs give the minimum speed for the flap setting indicated by each bug - retract before that and you will be in the yellow area. Descending they indicate the maximum speed for the bugged setting, e.g. you should extend F15 after passing the F15 bug, but before hitting the yellow caution area for slats.Tom

Share this post


Link to post
Share on other sites
Climbing out, the bugs give the minimum speed for the flap setting indicated by each bug - retract before that and you will be in the yellow area. Descending they indicate the maximum speed for the bugged setting, e.g. you should extend F15 after passing the F15 bug, but before hitting the yellow caution area for slats.
Still unclear. When climbing with Flaps 18 for instance, I have -FE28 well above on the speed tape in certain situations. If it were like you describe, I'd expect there to be a lower flaps setting (e.g. -FR10) like in the Boeings. Besides, I'd be way too slow with my flaps 18 only!Same for approach: I have situations where -FE50 passes the speed bug from below but I'm only at flaps 35 or so and that's the final setting for landing flaps, no word about flaps 50!.I tried to handle it like in the Boeings on my first approach attempt and was puzzled what -FE bugs came along on the speed tape and at what speeds and how many there were at the same time! I was instantly unable to decide at what point to change flaps settings. Then I read the manual several times and still cannot properly figure out what all the simultanously displayed -FE bugs mean exactly.So, it can't be exactly how you say, or I misunderstand something terribly wrong: I'm used to what Boeings and Airbuses usually display, namely some sort of flaps maneuvering speed. The Airbus in addition to the Boeings has the -FEnext symbol which in my understanding is an equivalent for Vfe-max for a given flaps setting, but both display maneuvering speeds so when on approach at flaps up passing the "UP" flag, flaps 1 (or more) are set, and the next lower flaps (e.g. -2) is displayed _below_ the current airspeed. Same for climbing where I have the next _lower_ flaps bug above at the speed tape, passing it means retraction.I was told the MD-11 is not a Boeing (what surprise), and that the bugs are not meant for the "traditional" flaps extension/retraction schedule - something I can hardly believe IMHO. Somehow it's different on the MD-11, I know, but I cannot think it's _that_ different.Note that I guess I faintly understand what -FR and -SR and -GR mean, namely the speed when gear/flaps/slats should be retracted. The issue I have is mainly with the -FE and -SE and -GE speeds, where I can imagine that -GE is a maximum speed indication, but -FE and -SE are still a riddle since the bugs serve two functions: one that shows the flaps extension limit is exceeded (amber speed bug), and another which I don't know yet and need help.Andreas

Share this post


Link to post
Share on other sites
Same for approach: I have situations where -FE50 passes the speed bug from below but I'm only at flaps 35 or so and that's the final setting for landing flaps, no word about flaps 50!.
Its not difficult to understand at all, its telling you that you could use 50 degrees flap safely now if you wish. Whether you do or not is up to the pilots training to decide.

Share this post


Link to post
Share on other sites
Still unclear. When climbing with Flaps 18 for instance, I have -FE28 well above on the speed tape in certain situations. If it were like you describe, I'd expect there to be a lower flaps setting (e.g. -FR10) like in the Boeings. Besides, I'd be way too slow with my flaps 18 only!
The relevant bugs on climbout are "FR" and "SR" - regardless of dial-a-flap setting.Tom

Share this post


Link to post
Share on other sites
Its not difficult to understand at all, its telling you that you could use 50 degrees flap safely now if you wish. Whether you do or not is up to the pilots training to decide.
This doesn't help me much:
you could use 50 degrees flap safely now if you wish
The point where I consider to use flaps "safely" is any speed below Vfemax. The flaps bugs reflect this in that they go amber once Vfemax is exceeded.Leaves the question: What does e.g. "-FE28" indicate? Cannot be the flaps maneuver speed since as I said on takeoff with flaps 18, I have -FE28 upwards on the speedtape, and on landing, -FE50 passes by while decelerating with flaps 35.So, what exactly do the -FE bugs indicate?
Whether you do or not is up to the pilots training to decide.
Whether and when to extend flaps is not only based on decision but on speed limits as well. To fly economically and within the flight envelope and stay on the safe side it is imperative to know the maneuver speed for a given configuration. Get below that speed and you're in for some troubles.So, are the -FE bugs the maneuver speeds? I can hardly imagine (see above)...Andreas

Share this post


Link to post
Share on other sites

Manoeuvring speed for flaps less than 28 is Vmin+20, for flaps 28 Vmin+5, for landing flaps Vapp.One simple example, let's say you are flying 220 knots with slats extended and you want to reduce to 180 knot; Top amber band is 170 knots for example (Vmin), you should select flaps 15 in order to create a 20 knots margin between your speed of 180 knots and Vmin.Floris

Share this post


Link to post
Share on other sites

Okay, I'll try to get some screenshots of different situations and update this thread at a later time.Thank you for your help so far.Andreas

Share this post


Link to post
Share on other sites