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Approach Woes

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GrandpaKim View Drop Down
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Joined: August-28-2013
Location: Calgary
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GrandpaKim Quote  Post ReplyReply Direct Link To This Post Topic: Approach Woes
    Posted: April-20-2017 at 8:19pm
No, it's not my flying and it's not setting up the FP properly, it is getting from arrival to approach that my knowledge lets me down.

Just today I was hand flying a DME arc followed by AP controlled ILS approach in the F1 B-200.  The arc went stunningly well, perhaps even good enough to pass a RL checkride so I elected to see what would go wrong this time when I gave the approach to Otto.

I started the turn to final then turned on the AP.  As per normal it went to ROL mode and tried to level the wings.  No surprise, I expected that and quickly activated APP.  She quickly re-established the bank and captured the localizer.  All good so far, but here it comes. 

This IF and turn are so far out, the PFD shows "No GS" where to GS bug should be, I am that far below it.  The plane begins climbing... and climbing.  The climb became so steep, I was in serious danger of stalling especially considering I was at about 80% N1.  (Just so you know, I had the altitude bug set for the next lower altitude step and was flying the published altitude for the current leg.  VS was off, ALT was off.)  I quickly went to NAV mode and VS mode and got things under control.  When the GS finally registered, I re-engaged APP mode and all was well.

This is just a sample of the kind of gong show I go through trying to fly an approach with autopilot.  Another thing that can mess me up is the (often? usual?) discontinuity between the end of the arrival and the beginning of the approach.  It seems too that activating an approach too early can cause unexpected results.

What I'm looking for is step by step procedures for getting correct results.  This includes tips on the flight plan itself and manipulating it as well as proper use of the autopilot.

Thanks
Kim
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quantumleap View Drop Down
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Joined: May-10-2005
Location: NL, Canada
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Post Options Post Options   Thanks (0) Thanks(0)   Quote quantumleap Quote  Post ReplyReply Direct Link To This Post Posted: June-28-2017 at 3:28pm
Which aircraft?

Jeff


Check out my aviation photography and digital art at Photisify
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Flying Dutchman View Drop Down
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Joined: February-28-2011
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Flying Dutchman Quote  Post ReplyReply Direct Link To This Post Posted: July-05-2017 at 3:18pm
"followed by AP controlled ILS approach in the F1 B-200."
Best regards, Jaap.
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Yoda View Drop Down
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Joined: November-25-2004
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Yoda Quote  Post ReplyReply Direct Link To This Post Posted: July-06-2017 at 10:21am
Kim,
 
It sounds to me like you just went to APP mode too early. There are a lot of different ideas about when to select APP mode, but what's worked best for me is waiting until the GS/GP bug is slightly above one dot above center. I try to be at APPCH flaps and 140 KIAS before that point, but if you haven't dropped the flaps by then, do it immediately after selecting APP. You'll balloon some (just like the real aircraft), and still pitch over onto the glide slope/glide path on time.
 
As a general practice, I lower the landing gear as the GS/GP bug reaches center, so that when the airplane pitches down, drag of the landing gear offsets the descent acceleration. This way you only need to adjust power once to establish a stabilized approach. If you drop the gear right before FAF, for example, you have to adjust power twice...once for the initial descent on the glide slope/glide path and then again when the gear comes down. Set power to maintain at least 121 KIAS (blue line), so if you need to execute a missed approach, you're already at the best climb speed or decelerating to it.
 
A note on setting landing power: leave the prop levers at the cruise setting until touchdown or you have to go around. The reason for this is to keep the props at or on the governors for a quicker transition to reverse. There's no harm done if you push the levers forward early, but it's good practice to wait, and you'll be glad you did when you're landing on shorter runways.
 
At the G1000's "500" warning, switch off prop sync and dump the rest of the flaps. The airplane will pitch up fairly sharply, so hold her on the glide slope with forward pressure on the yoke...and I mean commanding pressure. Here's where you can cause yourself to have to land long or dive for the runway. If you had power set properly on the previous phase of the approach, you shouldn't need to adjust it here. The plane will slow to around 100-105 KIAS, which is exactly what you want.
 
By the book, the Vref speeds are 95 KIAS or less, but that's not TOUCH DOWN speed, that's the target speed for 50 feet ABOVE touch down. So, as you start your flare, leave the power as is, and aim for the fixed distance markers (or the patch of tire marks that shows where the "consensus landing point" is), and let the airspeed bleed off. The airplane will slow naturally, and should touch down at around 86-88 KIAS. NOW push your prop levers full forward, and immediately pull the power levers into reverse.
 
Don't get on the brakes until you're below 70 KIAS, and use them sparingly at that.
 
With regard to discontinuities, I've made it a habit to plan my flight all the way through the preferred approach, and to put the initial approach fix into my flight plan. That way, I can activate the approach when I'm on the leg of the FPL that's taking me to the IAF.
 
Likewise, at the beginning of the flight plan, I build my FPL so that the first waypoint is the transition off the DP.
 
When flying online, it's been my experience that ATC is fairly forgiving if you want to fly an approach other than the one they've been giving to other aircraft landing at your destination, so long as it fits the flow of traffic. If the runway in use has changed while you were enroute, ask for vectors to the initial, and they're almost always happy to oblige. Note that you're still responsible for terrain avoidance, so you should have TERRAIN enabled on the MFD, and you should use it to monitor your flight path. If it looks like ATC is vectoring you into cumulogranite, speak up right away.
 
Hope this helps!
Respectfully,

Kurt

"Still proudly making Jim Rhoads crazy!"
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