cws alert still coming on on 737 NG approach

[Guest lenrow]

hello,I have changed my joystick to a new logitech from MS sidewinder thinking it was spiking signals that uncaptured the GS and gave the cws yellow alert with default to LOC approach but its still happening. Always able to recap the GS with another tap or two on the app but its awkward. Once within ten miles the GS holds well....kind of like the gs signal is stronger closer in but does the FS have such a dwindling signal or is it all or none? My approach speeds and flap settings are are per the check list and I'm not touching the control wheel. Happens at most ILSs and never with the 747. any ideas of maintaining a good Glideslope capture from 10 to 20 miles on the ILS or am I hoping for too much? thanksdoug wornell, CFII

[downscc 1,327]

The default FS ILS range is 27nm, which applies to LOC/GS/DME equally. Most approaches are designed for GS capture at FAF (final approach fix) about 5 nm and about 2000 agl, or perhaps a few miles further (LOC capture can be over 40nm out in some published transitions). Regardless, I can't think of an obvious reason why your GS trips. I have flown captured to the glideslope in the 737NG from about 15nm out with no glitch at KLAS (ILS25L outside LARRE), airspeed close to the 5-deg flap mark (approx 160kts). The AP holds GS during flap and gear deployment and speed changes no problem. I use a MS sidewinder joystick. It doesn't make sense that you have the problem only beyond 10 nm, unless it has something to do with aircraft speed or configuration. If it were hardware I'd expect it to be a problem at any point on the approach. 'Just my humble opinion.

[Guest lenrow]

thanks Dan. I agree with you and frankly must admit I probably fly faster than the designated flap speeds on base and early final as it seems the airplane's pitch attitude and angle of attack is abnormally high at those settings due to the slow airspeed and lack of lift. It may be that I'm adding flaps outside the 10 mile mark after GS capture at too high a speed and the trim is not able to handle it thus it breaks from the GS. Your comments appreciated. Tell me the speeds you use on base and final, through the localizer and then the GS. Doug W.

[downscc 1,327]

<>Depends on weight of course, in the -700 I select either 30 or 40 deg for a Vref close to 130kts. Unless otherwise instructed by the STAR or ATC, sometimes I slow to 210kts after entering the terminal area (about 30 nm out) for final approach vectors (maybe closer if changes in heading that are not going to be required), 170kts/5deg flaps for base or IAF (Initial Approach Fix), when GS comes alive (GS indicator turns into a solid diamond) I drop gear and go to 15deg flaps and whatever speed corresponds to that tick mark on the speed tap (around 140 kts), then at GS capture in add the remaining flaps (30 or 40 deg) and slow to Vref+5. I picked this up from a real world 737 driver in this forum a couple of months ago and works for me.Some terminal areas are much larger and busier, and speed is set by ATC who is trying to keep a smooth flow and separation such that runway use is maximized and vectoring for separation is minimized. Regardless, the speed you fly after IAF (Initial Approach Fix) is based on equipment and conditions rather than ATC spacing, although they will occasionally ask you to keep the speed up or slow down as long as you can.

[Guest lenrow]

thanks for your time, Dan. I'll give that a try.doug wornellktiw

[ronzie 21]

"...Regardless, the speed you fly after IAF (Initial Approach Fix) is based on equipment and conditions rather than ATC spacing, although they will occasionally ask you to keep the speed up or slow down as long as you can."Hi, Dan:I think it is the FAF rather than IAF where the aircraft condition and landing performance curve dominates the speed for final. ATC has to give pilot preference after that point but they can request an expedited landing and runway departure.

[Guest lenrow]

thanks for the help,Does anybody else feel that the recommended approach speeds/flap (regardless of fuel wt.) for the 737-700 sim model give a pitched up airplane attitude that is unrealistic...particularly before decent from GS capture? It seems for me that unfortunately flying any faster...and at a more realistic attitude, leads to a situation where the trim is not able to compensate for any further flap input after GS capture and a release happens with a control steering alert.thanks, I want this to work for me and I'm just not there yet doug Wornell, CFII, KTIW