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Guest Captain Barfbag

HELP! Keep landing in water. Need Approach Hold help in Boeing.

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Okay, here's the situation.I'm in a Boeing 737-400. I want to fly an autopilot Approach Hold landing into KSFO but I keep landing in the water.I'm about 1,800 feet around 20 miles out. I got the glideslope on my HSI. I press the APR button with autopilot armed. And I always plummet into the sea.Is there a trick to using the APR button?Do I disable all other autopilot switches (heading, altitude, IAS) before pressing APR? When should I press APR for the first time? Should autopilot do all of the work in Approach Hold mode?Please help me someone!In a similar question, can you provide quick tips on flying this in manually? I understand I must line up the purple "runway" into the centerline by making small heading adjustments. Once centered, how do I know if I'm the right altitude? Do I just start descenting and the purple indicator on the side of the HSI lowers appropriately?Aigh!Thanks very much! Bison

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A silly questio maybe, but are you sure thatyou have tuned the right ILS frequency ?You don't have to disable any other buttons in appr mode.The auto pilot does not do all work for you. It will keepyou on the right heading and locate you in the middle ofthe glide slope. However, you must handle speed, flaps, gearsetc. by your own. If you don't keep enough speed up, youwill certainly get into the water.If you do it manually, you can still use the ILS indicationson your instrument to see that your glideslope is correct andthen adjust the height and angle for your self.If you do it visually, you have to use the VASI or PAPI-systemon the airport. That is the kind of signs that you can seeat the beginning of the runway. If you are too high, you havefor instance 4 white lights visible. If you are too low, youwill see 4 red lights. Correct altitude is indicated by two whiteand two red lights.Best regards Bj

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A few pointers...Check the ILS frequency and course setting. Make sure they're correct first.For KSFO :Runway Length Surface ILS ID ILS Freq. ILS Hdg.10L 11870 Asphalt *** *** ***28R 11870 Asphalt IGWQ 111.70 28210R 10600 Asphalt *** *** ***28L 10600 Asphalt ISFO 109.55 2821R 9407 Asphalt *** *** ***19L 9407 Asphalt ISIA 108.90 1921L 7501 Asphalt *** *** ***19R 7501 Asphalt *** *** ***Note that none of these approaches are really over the sea, which runway were you using?At 20 miles out the ILS would have you at about 6000ft, most approaches start (I'm generalising here) at about 10nm and 3000ft.Use the autopilot hdg and alt hold modes to get you 15nm out and slightly to one side of the localiser and at 3000ft. Point towards the localiser (intercept angle of about 30 degrees or less) and arm the approach mode. The apr button should light up but the others should stay on. When the aircraft intercepts the localiser the hdg hold will drop out and the aircraft will track the localiser. When the glideslope comes down (the purple dot reaches the white mark on the vertical scale) the alt hold will drop out and the aircraft will follow the glideslope.Don't forget to control your speed, rough figures for you to aim for :210 (1 - 5 deg flap) before intercepting the localiser180 (5 - 15 deg flap) on localiser intercepting the glideslopeGear down when intercepting the glideslope.Being the speed back to about 140 ish (30 - 40 deg flap) as you reach the runway.I personally don't think the autoland is very good and tend to take the autopilot out at 500ft. I then lose the autothrottle at 200ft and manually fly the last few seconds. Reduce throttle to idle at about 50ft and start bringing the nose up (until the runway just disappears under the nose) at about 20ft.To fly it manually do just as you said.Here's a quick illustration of what I mean, this is an approach to KSFO rwy 28R.15nm out HDG and ALT holding 30 deg intercept and 3000ft.APR Armed...http://forums.avsim.com/user_files/14017.jpgAutopilot is turning to intercept the localiser, HDG has dropped out and I've reduced the speed to 180kts.http://forums.avsim.com/user_files/14018.jpgGlideslope active, the autopilot is in the process of capturing the glideslope (it's a bit wild for a while but it calms down eventually). Note the ALT mode has been removed. Gear is down with a bit more flap.http://forums.avsim.com/user_files/14019.jpgHere we are 6nm out, autopilot captured the localiser and glideslope and speed. Gear is down, full flaps are selected, autobrakes on 2 and spoilers armed (it's embarrassing to land perfectly but run off the end of the runway - and expensive).http://forums.avsim.com/user_files/14022.jpgTwo final shots:Top left is very short final, autopilot is off and I've just switched off the autothrottle.Bottom right is the dying few seconds of flight, throttles to idle, nose up and just letting it settle on the main gear.http://forums.avsim.com/user_files/14023.jpgHope this helps,Ian

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the 737 is one i fly alot; i keep ias at 140 +-, keep the little purple arrow on the right of the HSI at the center mark [above/below glideslope indication]gradually reducing speed , adding last flaps[full] usually over the middle marker, so i'm over the threshold at mid to low 120"s. pull power off and gradually raise nose towards +10 degrees keeping sinkrate at 300 fpm. should settle down real sweetly. as an aside, if you're not already using it, search for the "pa a320 cfm56" sound set. though it says a320, the sound set is REALLY close to the 737, the gear sounds in the cockpit with "wind noise" while the gear is in transit is great. reverse also sounds great. helps if you have a "powered" set of speakers. enjoy. tt

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With respect, I think that the proper touchdown attitude is approximately five degrees nose up or a bit less. Ideally you should keep your speed around 135 knots and attitude 2-3 degrees until over the threshold. This gives -700 v/s. Then cut the throttles (RA 50-70 feet) and start flaring so as to touchdown with -300 V/S. This is the normal profile more or less for a 737 but with the exception of Vref the rest I think applies more or less for all Boeings.Edit:This means that I am with Ian on this one.Regards

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A comment on the touch, if you watch any 737 pilot they will have the VSI at almost 0 when they touch. In the last 10 feet is where it all counts. I only speak from a video of the 737 flight deck but thats how they seemed to do it.Also the touch speed varies on your weight alot. And a normal landing is done on flap 30.The speeds I use on APP areFlap 5 180ktsFlap 15 150ktsFlap 20 140Flap 30 130 ish (being the landing speed based on weight)Just a passing comment, I tried -300 and that was a hard landing for me.All the best, I know that was off topic.Simon

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Two other things:Check your fuel load. If you're taking off with full tanks, turning and coming back, then you've got too much fuel on board. On a lot of aircraft the APR hold will not work if you're overweight. Unless I'm going a long way, I start with 40% in all tanks on a 737. (And watch the fries and burgers, too!)The APR for altitude will only acquire if you are BELOW the glide slope. This is the way ATC usually vectors you in. If you're above, the APR will not catch the glide slope. I usually engage the APR when the glideslope indicator is halfway between the center and the top of the bar.

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