FAF to MAP Speeds

Discussion in 'Cleared for the Approach' started by 2nd505th, Nov 30, 2018.

  1. dtuuri

    dtuuri En-Route

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    "Or 3nm, whichever comes last?"
     
  2. MooneyDriver78

    MooneyDriver78 Pattern Altitude

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    How does aerodynamics different between pistons vs jets for best glide (ie no power)? They both have drag coefficients, etc.
     
  3. James331

    James331 Touchdown! Greaser!

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    Where did I say that?

    It’s common sense, if those are the two cues to drop gear and configure, if you’re positioned waaaay out there and it comes to one dot and you’re still 10nm or something to the FAF you’re not going to drop the gear, if ya lack that common sense you probably shouldn’t be taking the checkride.
     
  4. MooneyDriver78

    MooneyDriver78 Pattern Altitude

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    I do, the fact you point to an article that doesn’t even reference best glide speed , which is what we’re talking about tells me you’re the clueless one.
    Maybe you should find the authors of the 2 presentations I screenshot and tell them they need remedial training.
     
  5. dtuuri

    dtuuri En-Route

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    Don't pay attention to coefficients, they're for engineers. Fuel flow follows thrust in jets, power in pistons. Max endurance is a function of power in pistons, thrust in jets.
     
  6. MooneyDriver78

    MooneyDriver78 Pattern Altitude

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    We’re talking about best glide...no power, no fuel flow....
     
  7. dtuuri

    dtuuri En-Route

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    No, we're talking about the "back side of the power curve", which for pistons is found on a power required chart, jets on a thrust required chart. Your posted chart has to do with "coefficients". Leave it for engineers.
     
  8. kgruber

    kgruber En-Route

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    For what jets do you possess a type rating?
     
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  9. midlifeflyer

    midlifeflyer Final Approach

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    Not having flown outside US airspace (where I know I would need to understand and utilize several procedures different than what I am used to) is a much better explanation than being a "young kid with no appreciation." :D
     
  10. midlifeflyer

    midlifeflyer Final Approach

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    WAG - he means the PFAF not, say, intercepting an LPV glidepath 50 miles from the threshold.
     
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  11. dtuuri

    dtuuri En-Route

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    I just think pilots need to be flexible and prepared to go with the flow when safe. Dogmatically dropping the gear one dot below without regard to distance and altitude isn't necessarily a good SOP, if that's what's being advocated. Picking it up again isn't, likewise, a bad thing if it helps out the guy behind. The cost is nothing. Big caveat here: anytime a checklist item has been undone, imo, the entire checklist needs to be repeated at the appropriate time. That's my SOP. I'd also keep a finger on the undone switch until then as a matter of technique.
     
  12. James331

    James331 Touchdown! Greaser!

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    You don’t read well, go back over what I wrote slowly and sound the words out, let me know if you need anymore help.

    Once you’re basically on the FAF, pulling the gear back up is straight stupid, if it’s that cramped someone needs to go around.
     
  13. dmspilot

    dmspilot En-Route

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    We are? You perform ILS approaches without power?

    Suggest you try learning from a book, not random slideshows you find with Google.

    By the way, the name of the slideshow you screenshotted is "Takeoff Performance: Jet Aircraft Performance", not "Mooney Descent and Glide Performance".

    edited to add linky
     
    Last edited: Dec 15, 2018
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  14. dtuuri

    dtuuri En-Route

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    Let's take it from the top:
    Help me see where you don't say lower the gear "1 dot" below the GS? Let me know if you need help spelling "preform".
     
  15. dtuuri

    dtuuri En-Route

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    I knew it had to be for jets! Do you have a link? I'd like to go through it looking for mistakes.
     
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  16. James331

    James331 Touchdown! Greaser!

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    I know I’m always one to argue, but are you just messing with me? Lol

     
  17. midlifeflyer

    midlifeflyer Final Approach

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    I'll disagree on one point. While flexibility to handle highly unusual situations is always important, "dogmatically" dropping the gear at the same point, here, crossing the FAF on an IFR approach, forms a habit which decreases the risk of a gear-up landing.
     
  18. Checkout_my_Six

    Checkout_my_Six Final Approach

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    till ATC throws a monkey into the works and "makes" you do something different .....and you're outta your normal routine and then the gear doesn't come down....but no one dies.;)
     
  19. midlifeflyer

    midlifeflyer Final Approach

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    Like everything in aviation, we're talking about lowering risk, not guaranteeing its elimination. That's why I phrased it the way I did.

    One of the things that I've seen happen when you are outta your normal routine is a level of discomfort. Even that can act as a constant reminder of what's missing. That's one of the effects of habits. Breaking them makes us feel uncomfortable.
     
  20. Checkout_my_Six

    Checkout_my_Six Final Approach

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    yup...that too...but there are no guarantees in this human factors/interface stuff. :confused:
     
  21. dtuuri

    dtuuri En-Route

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    Eh, could be. Have a carrot, Doc. :D
    That is not a disagreement. Always dropping the gear at the FAF isn't the same as always dropping it one "1 dot below", which is what I was reading and which caused Hank to then need to raise the gear up again. There may be a good reason to put the wheels down earlier than the normal habit, keeping a higher power setting under a low speed restriction for anti-ice reasons comes to mind, but if you aren't near the FAF and a new reason comes up to retract the gear, like a big change in speed restriction--I'm not going to cast aspersions on the PIC unless s/he forgets to put it back down again, which won't happen with good operating procedures.
     
  22. midlifeflyer

    midlifeflyer Final Approach

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    You and I agree. But I think @James331 does too and wasn't recommending gear extension 50 miles from the airport if you happen to intercept the glidepath at 15,000 AGL
     
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  23. PaulS

    PaulS Final Approach

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    Cute argument, but confusing the crap out of me, I'm training for IR now, what I've been taught is plane configured for glide slope when glide slope becomes active, full dot visible (PFD HSI, which would correspond to GS needle on top dot as it starts coming in). This assumes you are at FAF crossing altitude at the time. If ATC has kept you high for some reason then you need to realize that and adjust accordingly. For non precision you should be configured for the final approach by 2 nm before the FAF, no gear down for me, but this means slowing to 100 knots by the FAF and having 50% flaps out there before you begin descending at the FAF.

    All that said, you need to add ATC into the mix, my limited experience is that they always chime in when you are trying to do something or trying to figure out something adding a new twist or disrupting your flow. Not their fault (most of the time) but they need to be dealt with and you generally need to do what you are told.

    I don't fly retracts, but dropping the gear at the FAF seems like a destabilizing move for the approach as it is a configuration change, adding drag, requiring a possible pitch change and power change. Seems getting it done 2 or 3 miles before the FAF is a better procedure. But what do I know?
     
  24. dtuuri

    dtuuri En-Route

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    I think you're looking through a more powerful microscope than me. "FAF", "PFAF", are loose terms here. When the GS centers you want to have timed the configuration changes so the result is a nice stable descent with minimum power adjustments. Normally this happens at the PFAF on an ILS and no further changes to the landing gear should occur. It's when a choice was made to drop the gear way before that, for some reason or dogma, that I'm saying it's ok to change your mind and retract it. Just have an SOP that results in putting it back down again in that case. For me, it's holding the gear switch as a reminder and running the before landing checklist again if already done: "Landing gear down, landing checklist" is one word in my vocabulary.
     
  25. midlifeflyer

    midlifeflyer Final Approach

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    You might be very surprised, then.

    Saw Dave's comment as I was typing this, so it's a bit repetitious.

    Based on about the half dozen or more different retractable singles I've flown and taught in, in most "normal " cases, you set up your retract for level flight at your final approach segment speed. If you drop the gear as you approach the glidepath intercept, and do nothing else, the airplane will capture and descend on the glidepath at the same speed. That, of course is subject to the normal adjustment in pitch and power you'd make after being established on any stable descent down an ILS.

    I remember the first time a showed this to a nonbeliever who was used to making a bunch of changes when putting down the gear, never realizing the net was where he would have been without making any of them. "That's not fair!" was his comment.
     
  26. PaulS

    PaulS Final Approach

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    Ok, I get what Dave is saying, and it sounds fine to me. Are you saying you time the gear drop to coincide with the GS intercept, so that the gear is down at or just before this point which will coincide with your normal pitch and power adjustment for the descent? For the record, I don't see myself nor do I really have the desire at this point to fly a retract, more curious than anything else.
     
  27. AKBill

    AKBill Pattern Altitude

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    Interesting thread. I spent about an hour on YouTube watching training videos on how to read IFR approach plates just to follow what you all were talking about. Got an education.

    I'm just a humble VFR pilot of 23 years...:rolleyes:
     
  28. midlifeflyer

    midlifeflyer Final Approach

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    That's pretty close. The timing is not measuring a football field with a micrometer. The gear down is usually done a dot or so before intercept to allow the change to take place. And the "normal" pitch and power adjustment has already been made, exept perhaps for a small nudge on the yoke to get it started.

    To give an example, if you learned to create a pitch/power/configuration table, you have target pitch/power listings for various phases, including approach level and glidepath descent (if you don't you're probably working too hard). Target airspeed is the same for both. If you fly the FAS at 90 KIAS, approach level is also 90 KIAS.

    In the "typical" fixed gear single, you get in your approach level configuration before joining the FAC and, as you intercept the glidepath, change to the glidepath descent configuration - typically a power change (there are, of course, exceptions). Hands off In a perfect world of no wind and stable air, that is all you need to do. The airplane pitches down about 3 degrees, the already established trim maintains the airspeed, and down you go on the glidepath. In the real world, it gets you close and you tweak as conditions require.

    In the "typical" retract single, I am doing the exact same thing as in the fixed gear except, the only difference between my approach level and glidepath descent configurations is the gear going down. Power doesn't change. The drag takes care of establishing the descent.
     
  29. jordane93

    jordane93 Final Approach

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    If done correctly, you don’t need to touch power until you add the last set of flaps in the CRJ. It’s all about energy management. I used to jockey the thrust levers a lot on approach until a check airman showed me I really didn’t need to touch the power until we add the finals flaps.
     
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  30. Bill Watson

    Bill Watson Pattern Altitude

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    They do need remedial training. Wouldn’t be the first time.

    Best L/D and Max Endurance are not the same speeds. In a glide, best L/D is best angle of descent and will result in Max Range in still air. Max Endurance is actually minimum sink rate, think min FPM down in a glide, and it always occurs at a slower speed than best L/D. Always.

    The article referenced doesn’t call out L/D by name presumably because airplane people talk about Best Range (point D I recall) which is one in the same in still air.

    I understand the best L/D generally corresponds to Vy and Miniumum Sink General corresponds to Vx but not sure the relationship is exact.

    Understanding the relations between best L/D and Min Sink is important in the real world where there is always wind. For Max Range, you want to fly faster than best L/D with a headwind, slower than best L/D with a helping tailwind.

    No jet experience here - this is glider stuff! But it’s true on all the airframes.


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  31. midlifeflyer

    midlifeflyer Final Approach

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    Not having had the experience, I didn't know if it went beyond piston singles. Thanks.

    It's not just approaches. I'd say that by far the most common thing I see when I do flight reviews and IPCs is pilots working so much harder than they need to. One of the best examples I've seen on the subject is Jason Miller's video on the commercial lazy 8s (I linked rather than embedded because it's off-topic). It's described in most training texts as a maneuver in which the pilot does a lot of work. He does next to none. I couldn't believe it myself until I tried it.
     
  32. MauleSkinner

    MauleSkinner Final Approach

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    Yup...turboprops, jets, they’re all still airplanes. ;)
    I’ll have to watch the Lazy 8 video...I used to be able to do them by letting go of the yoke from the 45-degree point to the 180-degree point of each half.
     
  33. jordane93

    jordane93 Final Approach

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    There’s a reason why lazy 8s are called lazy 8s! I struggled with that maneuver until my instructor basically told me to stop flying the plane so much.
     
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  34. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    OK, now tell me what the max endurance speed on a Mooney is.

    I understand that much just fine... But they don't publish a minimum sink speed for GA airplanes, and I've always heard that the best estimate for most of us is "about 5 knots below Vg" which would still put 80 knots behind the power curve in a Mooney. :dunno:

    There's no way they're exact... At gross, my Vx is 85, my Vy is 105, my vG is 91.5.

    Or do you mean they're offset by about the same amount, so my minimum sink would be 20 knots less than Vg?

    I'm still not sure I'm completely wrapping my head around the bottom of the power curve, though. If L/dmax gives us the most lift per drag, that means that if we were trying to maintain level flight, L/dmax would mean the lowest drag possible to keep the plane in the air and thus the lowest amount of power to overcome that drag. What am I missing? (besides my copy of Aerodynamics for Naval Aviators... Gonna have to find that.)
     
  35. dmspilot

    dmspilot En-Route

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    The least amount of thrust is required at L/Dmax, not power. Remember from physics that power is work done per unit of time. You fly slower, you do the same work in more time, less power is required. (If you were to double the thrust required, but cut the speed in half, the power required would be the same.)

    At a point, as an aircraft slows down below L/Dmax, the induced drag increases too rapidly to offset the slower rate at which the work must be done. That point would be where the minimum power is required, and it occurs roughly halfway between stall and L/Dmax.

    Screen Shot 2018-12-17 at 2.06.05 AM.png
     
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  36. aggie06

    aggie06 Pre-takeoff checklist

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    Agree that plenty of controlled fields will clear multiple aircraft on approach at the same time. Don’t be a jerk and slow to 60-65 at the FAF. I had a YouTube star do that in front of me on approach to MSN. Makes it hard to keep me and the other 8 planes behind me moving. On a long runway, 90 knots is perfectly safe.

    I’ve also been between 737s in what was technically IMC on approach into HOU. I kept gear and flaps up and maintained 140-145 in a 182RG until inside a mile. I like to think that was the right answer. Clearly it had turned into a visual approach but everyone was in and out of clouds until 2 or 3 miles out. Still plenty of time to be a pilot and slow it down before landing and getting out of the 737’s way.
     
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  37. Hank S

    Hank S En-Route

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    Sometimes, @aggie06 , you gotta do what you gotta do. Get too slow too soon with too much behind you is risking cancellation and being sent for a few laps in the hold while faster traffic lands.

    That's why, when Tower kept me at 7500msl and let me go 14 nm past the field before turning inbound, I kept the plane clean and descended at cruise power, working to slow down the last 2-3 miles. Which put me way out of normal procedure for dropping the gear. That's why I have two checks in the pattern (no pattern, no checks . . . ) AND a short final check of the mechanical indicator in the floor.
     
  38. MauleSkinner

    MauleSkinner Final Approach

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    And in the context of this thread, if 2500 feet of runway isn't "long", is recommend training and/or practice.
     
  39. Hank S

    Hank S En-Route

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    Few runways that short ha e insfrument approaches. Imwas based at a 3000' field with trees at both ends for 7 years, and have spent the last three years at a 3200' field with an open approach at one end and a wooded upslope from river to field at the other end. I've always used 90 mph downwind and base, roll wings level on final at 85 mph and slow to 70-75 mph depending on weight as I approach the field.

    I've never had trouble on an instrument landing, actual or simulated, coming in from the FAF at 105 mph = 90 knots.
     
  40. tspear

    tspear Pattern Altitude PoA Supporter

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    With RNAV the FAA has been rolling out LPV approaches to much smaller fields than preciously.

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