I was really light and since the FMC Approach page offered a 15 flaps Vref, I decided I'd land with 15 flaps. On short final the GPWS went crazy, repeating "too low flaps" incessantly. Is 15 flaps not allowed? If it is allowed, shouldn't my selection of LSK R1 (15 flaps) inhibit the GPWS message when I have flaps 15 deployed?Just curious. I normally use 30.Lee Hetherington (KBED)

Lee,According to my documentation flaps 30 or 40 are normal landing configurations. And the GPWS will announce flap warnings if not in landing configuration. But there should be a FLAP INHIBIT and GEAR INHIBIT for the GPWS for engine out landings and other abnormal landings. Would be great if PMDG would implement that in a later release!Hope it helps,

Not really an answer, Lee, but I was just wondering what your approach speed was, Lee??? I discovered yesterday that if your speed is greater than 150kts CAS, you shouldn't hear TOO LOW FLAPS at all (with your flaps at any setting).http://members.ozemail.com.au/~b744er/737/GPWS4b.GIFCheers.Ian.

Vref 15 was 128 I believe, so I was landing at 133 because of no wind. Granted, it sounds like I blew it landing at 15, but I was just testing things out. BTW, I found it odd that Vref 15 and Vref 30 were the same or within a few kts on the FMC, but perhaps that too is correct in this case as well.Lee Hetherington (KBED)

Hi Lee,The (Enhanced) Ground Proximity Warning System may be deactivated for approved non-normal procedures where the use of flaps at less than normal landing flap positions are specified. However after such procedure you have to make a logbook entry.Flap positions 30 and 40 are normal landing flap positions. Flaps 15 is used for some non-normal landing conditions. For example, upon recognition of an engine failure, in the event of a jammed elevator or aileron, jammed stabilizer, an asymmetry, no leading edge device(s), or leading edge devices not in programmed position with respect to the trailing edge flaps, trailing edge flaps malfunction (because of the time required to retract flaps electrically in event of a go-around), etc.Also you must inhibit the "ground proximity flap inhibit" switch to prevent a flap configuration warning.Do note that (from AOM): "Flaps 15 configuration results in a higher than normal pitch attitude. There is a tendency to push the nose down to obtain a normal visual sight picture. Use caution to avoid going below the normal glide path."Let's hope this shed some light on this issue.Off to sniff some kerosene! :-badteeth

Hi Lee,Indeed, this Next Generation babe has some nice speeds :)True, Vref 15 is not far away from Vref 30. Just look at the attached picture of a table with V(ref) speeds for 737-700.http://forums.avsim.net/user_files/29921.gifRegarding the Vref positioning i think I will give myself a freedom to clarify one thing a bit off topic. When the autothrottle is planned throughout approach and touchdown, position the internal bug to VREF + 5 knots, regardless of wind speed. The autothrottle design in the 737NG babes include automatic gust compensation. Therefore, it is not necessary to set gust or wind strength corrections on the speed selector. Altough it is sweet babe you must monitor her actions ;)If you discontinue autothrottle usage, you must immediatelly position the bug in correct place as described below.If you do it manually (thrust) you add 1/2 of steady wind and all the gust but NOT to exceed total addition of 20kts. Note that maximum addition of 15kts applies for 30/40 flaps landing in -800 and -900 series.Interesting thing is that in case of Flaps 15 landing in icing conditions you have to add "ice additive" of 10kts. This is in addition to the above mentioned wind additive. Example:Flaps 15 Vref=143Vref_ice=143+10=153Wind is 240@20EDIT: Runway in use 24 :)Wind addition is 10 (minimum 5 maximum 20)Target=Vref_ice+Wind_add=153+8=161ktsI need some more smell of jet fuel! Off I go! :-badteeth

>Vref 15 was 128 I believe, so I was landing at 133 because of>no wind. Granted, it sounds like I blew it landing at 15, but>I was just testing things out. BTW, I found it odd that Vref>15 and Vref 30 were the same or within a few kts on the FMC,>but perhaps that too is correct in this case as well.Vref is not the same as no warning speed, Vref is the min speed you can fly with with the flap setting, the warning generates from several things, tradio altitude, flap settings and landging gear possition, i dont remember when the flap warning will go out, but if Vref is 130 then 150 dont sound so wrong.DennisLicensed on the B737NG and the Airbus 319-321 as a technician (B1 and B2)

"Vref is not the same as no warning speed,..."I don't think anyone was saying this, Dennis. I was simply commenting on the fact that _IF_ Lee's approach speed had been above 150kts (possible at high weights and Flaps 15), then he wouldn't have got the TOO LOW FLAPS warning (as per the GPWS graph).Hope this clarifies things.Cheers.Ian.

>I don't think anyone was saying this, Dennis. I was simply>commenting on the fact that _IF_ Lee's approach speed had been>above 150kts (possible at high weights and Flaps 15), then he>wouldn't have got the TOO LOW FLAPS warning (as per the GPWS>graph).I missunderstood the question then, i understood it as he didnt understand why he got a warning when he had the right speed :-)That is how it goes when english isnt your main language heheDennisLicensed on the B737NG and the Airbus 319-321 as a technician (B1 and B2)

"Vref is the min speed you can fly with with the flap setting" - bluesy.No, Vref is the reference landing speed, ie. the speed of the aeroplane, in a specified landing configuration, at the point where it descends through the landing screen height (50ft) in the determination of the landing distance for manual landings.Taking an engine failure for example, the non-normal checklist (Quick Reference Handbook) states to plan a flap 15 landing and refers to a one engine inoperative approach checklist which includes setting the GPWS flap inhibit switch.Neil.

>"Vref is the min speed you can fly with with the flap>setting" - bluesy.>>No, Vref is the reference landing speed, ie. the speed of the>aeroplane, in a specified landing configuration, at the point>where it descends through the landing screen height (50ft) in>the determination of the landing distance for manual>landings.Same thing if you ask me, the min speed is Vref, you are not supposed to go under that because it is very close the the real min speed.>>Taking an engine failure for example, the non-normal checklist>(Quick Reference Handbook) states to plan a flap 15 landing>and refers to a one engine inoperative approach checklist>which includes setting the GPWS flap inhibit switch.That is to minimize the drag you have during landing, that way you will have an easier time getting back airborne with just one engine.DennisLicensed on the B737NG and the Airbus 319-321 as a technician (B1 and B2)

Isn't Vref by definition 1.3 Vso (stall speed)?BTW, it is pretty clear the GPWS I got with flaps 15 were perfectly appropriate. No PMDG bug there.Lee Hetherington (KBED)

>Isn't Vref by definition 1.3 Vso (stall speed)?1.2-1.3 Vso that is the stall speed yes, that is why you should never go below Vref and consider it a min speed (ok i understand that that is my opinion)>BTW, it is pretty clear the GPWS I got with flaps 15 were>perfectly appropriate. No PMDG bug there.It sure is :-D DennisLicensed on the B737NG and the Airbus 319-321 as a technician (B1 and B2)

Guys,>Isn't Vref by definition 1.3 Vso (stall speed)?What I gave earlier was the definition according to the Joint Aviation Requirements in Europe. Vref is indeed based on (for jets) 1.3Vs0 but another important consideration is that Vref must not be less than the minimum control speed in the landing configuration, Vmcl, which is determined by asymmetric flight characteristics.Regarding the use of flap 15:>That is to minimize the drag you have during landing, that way you>will have an easier time getting back airborne with just one engine.Yeah I covered that in my JAA ATPL exams! :-hah The higher approach speed also gives you a greater margin above Vmcl. An asymmetric go-around is done using flaps 1, so even less drag for better climb performance.Neil.