good@pixar (Never tell your copilot "Cheer up" during the takeoff roll.) (02/15/86)
I assume that most of you are aware of the 152 which tangled with the power lines on final at Ontario the other night. For those who don't know anything about it, nobody was hurt even though both men hung upside down for four hours. The plane dangled 80 feet off the ground by the propeller hub and the nose gear. My instructor has access to "inside" information on accident investigations and he called me a few minutes ago (ostensibly to tell me that the plane I use is available all day today -- during the biggest storm to hit the Bay Area this year. Do all instructors have such a sense of humor?) and told me what seems to have happened. Directional radio, such as localizers, glideslopes, etc, have false "lobes" on either side of the real beam. There can be several such lobes. Evidently the 152 in question, while on an night IFR training flight, was flying one of the lobes underneath the GS on approach. Thus they could have had the needle nailed to the bullseye and still tangled with the power line. Even if this was not the case, it is a good time to remind yourself of the good practice of checking your altitude at approach fixes, and especially as you cross the outer marker. The altitude at which the GS crosses the outer marker is plainly visible on your approach plate. Use it! Yours for more airports and fewer power lines, --Craig ...ucbvax!pixar!good
bam@sdchem.UUCP (Bret Marquis) (02/20/86)
Night IFR in a 152 is *really* defying death, no wonder they had trouble.. Bret Marquis (sdcsvax, ihnp4) bang!bam bam@NOSC.ARPA
djmolny@cuae2.UUCP (DJ Molny) (02/21/86)
In article <107@sdchema.sdchem.UUCP> bam@sdchema.UUCP (Bret Marquis) writes: >Night IFR in a 152 is *really* defying death, no wonder they had >trouble.. > They didn't get into trouble with the power lines, they just got, uh, "hung up." Sorry. -- Regards, DJ Molny ihnp4!cuae2!djmolny
brad@gcc-milo.ARPA (Brad Parker) (02/21/86)
In article <2473@pixar.pixar> good@pixar (Never tell your copilot "Cheer up" during the takeoff roll.) writes: > I assume that most of you are aware of the 152 which tangled with >the power lines on final at Ontario the other night. For those who don't >know anything about it, nobody was hurt... > Directional radio, such as localizers, glideslopes, etc, have false >"lobes" on either side of the real beam. There can be several such lobes. >Evidently the 152 in question, while on an night IFR training flight, was >flying one of the lobes underneath the GS on approach. Thus they could have >had the needle nailed to the bullseye and still tangled with the power line. I'm just a low time VFR pilot (so I could be wrong), but isn't the usual procedure to intercept the localizer before following the glideslope down? Isn't it impossible to get on such "false lobes" for both? (this may be obvious given that they ended up "hanging out" ;-) ) IFR old salts - what's the story here? -- J Bradford Parker General Computer (HyperDrive Beach) harvard!gcc-milo!brad "She said, 'Just drive.'" -heard on the radio.
good@pixar (Craig Good: About a half a bubble off level.) (02/24/86)
In article <474@gcc-milo.ARPA>, brad@gcc-milo.ARPA (Brad Parker) writes: > ... > I'm just a low time VFR pilot (so I could be wrong), but isn't the usual > procedure to intercept the localizer before following the glideslope down? > Isn't it impossible to get on such "false lobes" for both? (this may be > obvious given that they ended up "hanging out" ;-) ) > > IFR old salts - what's the story here? ( BTW, it was a 172, not a 152. Sorry about that.) Not having my IFR ticket yet (quite) I can't call myself an "old salt", but I have had plenty of chances to observe lobes on localizers. They seem to be more common than the lobes on the glideslope. At any rate, in many of the approaches we have flown during training we have intercepted the GS *before* reaching the localizer. This is actually quite handy since you can already have the rate of descent established by the time you have that other little needle to center. The only way to make sure you aren't on a GS lobe is to check your altitude at the approach fixes, especially the outer marker (although there are usually a couple of other approach fixes), against what it says on the approach plate. Of course, if an actuall salty old IFR pilot has another method he'd like to share with us... --Craig ...ucbvax!pixar!good
marcum@sun.uucp (Alan Marcum) (02/26/86)
> In article <474@gcc-milo.ARPA>, brad@gcc-milo.ARPA (Brad Parker) writes: > At any rate, in many of > the approaches we have flown during training we have intercepted the GS > *before* reaching the localizer. This is actually quite handy since you > can already have the rate of descent established by the time you have that > other little needle to center. If you begin descent on an ILS prior to getting "established on the localizer," you may fly through a granite (or steel or cement) cloud. An approach clearance could read, in part, "Fleetfoot 1234A is 5 miles from the outer marker. Turn left heading 330; maintain at or above 3000 until established on the localizer. Cleared ILS 30L approach." Now, if you're above 3000, and the glideslope needle starts coming in, fine, start the descent. Flying around (SF Bay Area), the clearance usually is something like "maintain 3000 until established" -- I'm already as low as I should be, anyway. So, the question becomes, "When am I established?" I learned that you're established when the localizer needle comes off the peg during intercept. I don't happen to have my FAR/AIM handy here, nor other descriptions of the ILS transmitter system. If I recall correctly, there are indeed lobes on the GS -- "false gs" -- but spurious localizer signals are detected by the receiver, and the flag on the omni head goes up. From my own experiences during training, a fals GS will indeed foul things up. I found one while learning about the ILS tracking abilities of the autopilot. The autopilot captured the localizer and a false GS. Both my instructor and I noticed we were a tad (!!) high at the outer marker, and we decided to let the A/P continue to fly the approach (we were in VMC) for demonstration, until things got a bit out-of-hand. -- Alan M. Marcum Sun Microsystems, Technical Consulting ...!{dual,ihnp4}!sun!nescorna!marcum Mountain View, California
LShilkoff.ES@XEROX.COM (02/26/86)
The proper procedure for an ILS approach is to intercept the localizer before interpreting any gildeslope information. The results could be fatal as they have been noted in various publications of NTSB reports on accidents involving false glideslope indications. Besides, the next time you try an approach at your nearby ILS, you'll find the controller will tell you, "Barnburner 1234 cleared runway 7 ILS approach. Maintain 4000 feet or above until intercepting the localizer". Larry
ths@lanl.ARPA (Ted Spitzmiller) (02/26/86)
> > I'm just a low time VFR pilot (so I could be wrong), but isn't the usual > > procedure to intercept the localizer before following the glideslope down? > > ..... in many of > the approaches we have flown during training we have intercepted the GS > *before* reaching the localizer. This is actually quite handy since you > can already have the rate of descent established by the time you have that > other little needle to center. > > --Craig As I mentioned in a previous posting, you should NOT begin the descent UNTIL you are established on the inbound course (LOC needle off the peg). If you are getting the GS before the LOC then one of a number of situations has occurred: o If you are on vectors, the controller is required to bring you into the LOC before GS intercept. This position is outside of a point 2 miles from the GS intercept, at the GS intercept altitude. This point is called the "approach gate". A controller may NOT position an aircraft to intercept the GS from above. o If you are flying a PT, you are not going out far enough from the OM before starting the PT. Generally 90 seconds is acceptable unless you have a lot of altitude to loose or there is a significant headwind on the outbound. One technique is to begin your OB timing over the OM but do not start the PT until the GS comes off the vertical peg and preferrably not until the GS needle centers. This will assure that even with a stiff headwind during the OB you will have enough time to intercept the GS from below and on the LOC. Perhaps some of the other "old salts" might have some other suggestions. Ted Spitzmiller
bl@hplabsb.UUCP (Bruce T. Lowerre) (02/27/86)
> In article <2473@pixar.pixar> good@pixar (Never tell your copilot "Cheer up" during the takeoff roll.) writes: > > I assume that most of you are aware of the 152 which tangled with > >the power lines on final at Ontario the other night. For those who don't > >know anything about it, nobody was hurt... > > Directional radio, such as localizers, glideslopes, etc, have false > >"lobes" on either side of the real beam. There can be several such lobes. > >Evidently the 152 in question, while on an night IFR training flight, was > >flying one of the lobes underneath the GS on approach. Thus they could have > >had the needle nailed to the bullseye and still tangled with the power line. > > I'm just a low time VFR pilot (so I could be wrong), but isn't the usual > procedure to intercept the localizer before following the glideslope down? > Isn't it impossible to get on such "false lobes" for both? (this may be > obvious given that they ended up "hanging out" ;-) ) > > IFR old salts - what's the story here? The localizer does not have false side lobes but does have a back course. The glide slope does have side lobes (actually above and below the true glide path). It works on a different principle than the localizer. The side lobe phenomenon is (or at least should be) well known to IFR pilots. If the accident was caused by tracking a side lobe, then the pilot made a procedural error in his initial approach. One must maintain a specified altitude until established on the localizer course and outside of the final approach fix (usually the outer marker). This altitude places the aircraft below the glide path. The glide path is then intercepted as the plane flies into it, and the descent is initiated. It's almost inconceivable that the plane could have intercepted a side lobe below the glide path unless he was 20 miles or more from the runway when he intercepted the localizer. A cross check on altitude is the glide slope altitude at the final approach fix which is published on the approach plate. If he descends below this altitude before reaching the final approcah fix, then he should know that something is wrong. Bruce T. Lowerre CFI
danny@joevax.UUCP (Dan Kahn) (02/27/86)
> > Not having my IFR ticket yet (quite) I can't call myself an "old salt", > but I have had plenty of chances to observe lobes on localizers. They seem to > be more common than the lobes on the glideslope. Problems with false lobes on the localizer are COMMON?! > At any rate, in many of > the approaches we have flown during training we have intercepted the GS > *before* reaching the localizer. This is actually quite handy since you > can already have the rate of descent established by the time you have that > other little needle to center. You do this OFTEN?!
daver@felix.UUCP (Dave Richards) (02/28/86)
> In article <2473@pixar.pixar> good@pixar (Never tell your copilot "Cheer up" during the takeoff roll.) writes: > > Directional radio, such as localizers, glideslopes, etc, have false > >"lobes" on either side of the real beam. There can be several such lobes. > >Evidently the 152 in question, while on an night IFR training flight, was > >flying one of the lobes underneath the GS on approach. Thus they could have > >had the needle nailed to the bullseye and still tangled with the power line. First of all it was a 172 (no bigee). I don't care what the given "reason" was for the accident, there is no excuse other than pilot error. They hit the power line at 85' AGL which doesn't sound too bad, but they were 2 miles from the runway! If the pilot was not instrument rated and they were making an ILS approach, then the instructor certainly must bear the blame. (as far as I know, conditions were VFR) I would say this guy's CFI rating should be suspended for a time while he undergoes re-testing. Just because no one was hurt this time doesn't mean they won't be killed next time. (not to mention the bad opinion of general aviation this type of thing promotes) That's my opinion. Dave Richards
epm0@bunny.UUCP (Erik P. Mintz) (03/02/86)
> First of all it was a 172 (no bigee). I don't care what the given "reason" > was for the accident, there is no excuse other than pilot error. They hit > the power line at 85' AGL which doesn't sound too bad, but they were 2 miles > from the runway! > . > . > That's my opinion. > > Dave Richards I agree, especially since regardless of what the glideslope was doing they should never have been below 200 agl (the minimum decision height for a category I ILS), unless the runway was in sight. -- Erik Mintz ARPA or CSnet : epm0%gte-labs.csnet@csnet-relay UUCP: ...harvard!bunny!epm0
hartsoug@oberon.UUCP (Mike Hartsough) (03/03/86)
> > > > Not having my IFR ticket yet (quite) I can't call myself an "old salt", > > but I have had plenty of chances to observe lobes on localizers. They seem to > > be more common than the lobes on the glideslope. > > Problems with false lobes on the localizer are COMMON?! > > > At any rate, in many of > > the approaches we have flown during training we have intercepted the GS > > *before* reaching the localizer. This is actually quite handy since you > > can already have the rate of descent established by the time you have that > > other little needle to center. > > You do this OFTEN?! I am a low-time VFR pilot, and while I am interested in this particular conversation, I have no idea of why you are so critical of this person's practices. I would appreciate it if you could be slightly more verbose in your responses, so that those of us without explicit IFR knowledge will be better able to follow the conversation, and perhaps learn what, if anything, is wrong with the aforementioned techniques. Thanks. -- Michael J. Hartsough hartsoug@oberon.UUCP It is to the interest of the commonwealth of mankind that there should be someone who is unconquered, someone against whom fortune has no power. ---- Seneca That's why I'm here.
hartsoug@oberon.UUCP (Mike Hartsough) (03/03/86)
> > Not having my IFR ticket yet (quite) I can't call myself an "old salt", > > but I have had plenty of chances to observe lobes on localizers. They seem to > > be more common than the lobes on the glideslope. > > Problems with false lobes on the localizer are COMMON?! > > > At any rate, in many of > > the approaches we have flown during training we have intercepted the GS > > *before* reaching the localizer. This is actually quite handy since you > > can already have the rate of descent established by the time you have that > > other little needle to center. > > You do this OFTEN?! I am a low-time VFR pilot, and while I am interested in this particular conversation, I have no idea of why you are so critical of this person's practices. I would appreciate it if you could be slightly more verbose in your responses, so that those of us without explicit IFR knowledge will be better able to follow the conversation, and perhaps learn what, if anything, is wrong with the aforementioned techniques. Thanks. -- Michael J. Hartsough hartsoug@oberon.UUCP It is to the interest of the commonwealth of mankind that there should be someone who is unconquered, someone against whom fortune has no power. ---- Seneca That's why I'm here.
good@pixar (Craig Good: Pixar Aeronautics Division) (03/03/86)
> You do this often???
It has happened, yes. It's the same thing that someone else mentioned
recently: the clearance is to maintain (for example) 3000' until established
on the localizer, but we are at 4000+ feet because we just came over the
hills East of Santa Rosa. Since he's cleared us to descend to 3000 we are
past the hills, but we are a little way out from actually intercepting the
glideslope. We intercept the GS, start the descent, the localizer needle
comes in, and we've had the needles both centered for about five hours :-)
by the time we reach the IAF. Check the altimiter: it's where it belongs.
Whew! Cheated Death again.
Thanks for all the responses. I've learned almost as much about how
careful you have to be to not be mis-understood on the net as I have about
flying approaches... :-}
--Craig
...ucbvax!pixar!goodmarcum@sun.uucp (Alan Marcum) (03/04/86)
> As I mentioned in a previous posting, you should NOT begin the descent UNTIL > you are established on the inbound course (LOC needle off the peg). If you > are getting the GS before the LOC then one of a number of situations has > occurred: > > o If you are on vectors, the controller is required to bring you > into the LOC before GS intercept. This position is outside of > a point 2 miles from the GS intercept, at the GS intercept altitude. > This point is called the "approach gate". A controller may NOT > position an aircraft to intercept the GS from above. > Ted Spitzmiller Ah, for a world where what should be is. I wish I had a buck for every time a controller's slam-dunked me onto the GS from above.... Yeah, I know -- they shouldn't. And, from an "Operation Raincheck," they know they shouldn't. But they do 'round here.... -- Alan M. Marcum Sun Microsystems, Technical Consulting ...!{dual,ihnp4}!sun!nescorna!marcum Mountain View, California
ladkin@kestrel.ARPA (Peter Ladkin) (03/07/86)
In article <3317@sun.uucp>, marcum@sun.uucp (Alan Marcum) writes: > Ah, for a world where what should be is. I wish I had a buck for every > time a controller's slam-dunked me onto the GS from above.... In the SF Bay Area, there is a slam-dunk (Bay Approach term, not mine) that is frequently used on commercial aircraft into SFO, where they bring them into the TCA from above, and right down on the GS. On my Instrument Flight Test, I was slam-dunked onto the Oakland 27R ILS from 7500 feet (down to intercept at 3500) in slightly over 4 miles, in an Archer. I've also had a Bay Approach controller cancel a VFR-on-top plan for me as soon as I was clear-of-clouds. Never mind 500 feet. Never mind a request. Peter Ladkin