What I have always wondered- step down fixes
#1
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Joined APC: Mar 2009
Position: Lunar Lander Commander
Posts: 158
What I have always wondered- step down fixes
Lets say you are on an approach with multiple step downs. Lets say you are cleared for the IAP and have 3 step downs to go to MDA. Now lets say you have the runway in sight because the weather is good so you get on the profile and because of this you go below minimum step down altitudes. Is this illegal? 91.175 says that you may descend below MDA/DH when the aircraft is in a position to land using normal maneuvers (3 degree VDP). Does this only apply to MDA/DH or to all minimum altitudes?
Should one always request the visual to CYA? And that is not KCYA if you know what I mean.
Thanks
Should one always request the visual to CYA? And that is not KCYA if you know what I mean.
Thanks
#3
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Joined APC: Mar 2009
Position: Lunar Lander Commander
Posts: 158
In our 135 opspecs their is no mention of this. We are single pilot/autopilot so we have no GOM or FTM so this would apply to all operations I guess. Or it would at least apply to 91 or 135 if not mentioned in opspecs.
Thanks
Thanks
#4
If you have been cleared for a specific instrument approach, you should comply with the step down altitudes associated with the approach unless otherwise authorized by ATC.
Crews arriving to ORD have been warned/violated for failing to do so. (In most cases the crews intercepted the glideslope and visually descended below the intermediate step downs before the FAF). Because they were not cleared for the visual they dont have much ground to stand on.
Remember, step downs may not just be fore obstacle avoidance. They might also be to avoid other protected airspace for airport underlying the approach. (A good example is the ILS 22L at EWR. The 2500' restriction over GIMEE is for traffic at 1500' departing from TEB.)
Crews arriving to ORD have been warned/violated for failing to do so. (In most cases the crews intercepted the glideslope and visually descended below the intermediate step downs before the FAF). Because they were not cleared for the visual they dont have much ground to stand on.
Remember, step downs may not just be fore obstacle avoidance. They might also be to avoid other protected airspace for airport underlying the approach. (A good example is the ILS 22L at EWR. The 2500' restriction over GIMEE is for traffic at 1500' departing from TEB.)
#5
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Joined APC: Mar 2009
Position: Lunar Lander Commander
Posts: 158
So this would be illegal than. I have a feeling it is even in VMC conditions when you can see the runway. 91.175 just talks about descent below MDA/DH not step down intermediate fix altitudes. So when inside the FAF is one thing but outside is quite another eh?
This is an easy one to screw up in the field.
BTW - This would really only apply to me with approaches like the BC into Santa Maria (KSMX) where it is circling only and the stepdowns are way above 3 degree's. On a normal approach it is not an issue if you are following a normal glide path in most cases.
This is an easy one to screw up in the field.
BTW - This would really only apply to me with approaches like the BC into Santa Maria (KSMX) where it is circling only and the stepdowns are way above 3 degree's. On a normal approach it is not an issue if you are following a normal glide path in most cases.
#6
If you are cleared for an instrument approach, you have to fly it, as depicted. Remember the IAP has the force of the FARs, as it is a FAR 97 procedure. If visual and cleared for contact or visual approach, you are OK to maneuver as needed, I see what you mean at KSMX, very steep final due to the antenna. It's similar to the controller, when spacing is getting too close, asking if the have the traffic or the field in sight, you do and he clears you for the visual. The visual eliminates his IFR spacing problem
GF
GF
#8
Yes you have to unless cleared for the visual. ORD is a perfect example where there might traffic beneath you.
But most airlines do CANPA for non-precision approaches now, and you will clear the vast majority of step downs if you use a 3 degree CANPA, or whatever glide angle is published on the chart. If you're too lazy to do step downs, start practicing CANPA...it works remarkably well. Actually it's safer, so not just a matter of being lazy. It helps to have a GPS to get an accurate groundspeed, but you can use atis winds to make a close estimate.
At SMX nobody is going to care.
But most airlines do CANPA for non-precision approaches now, and you will clear the vast majority of step downs if you use a 3 degree CANPA, or whatever glide angle is published on the chart. If you're too lazy to do step downs, start practicing CANPA...it works remarkably well. Actually it's safer, so not just a matter of being lazy. It helps to have a GPS to get an accurate groundspeed, but you can use atis winds to make a close estimate.
At SMX nobody is going to care.
#9
Kinda hard to fly a CANPA at KSMX. First, it is LOC-based, I not know that you can mix an FMS-derived vertical path with a LOC. Second, it is a V-MDA, not V-RWY (Collins terms)m so the path ends at the FAF. Last, the angle far exceeds 3 degrees, more like 10 degrees for a straight in.
GF
GF
#10
Kinda hard to fly a CANPA at KSMX. First, it is LOC-based, I not know that you can mix an FMS-derived vertical path with a LOC. Second, it is a V-MDA, not V-RWY (Collins terms)m so the path ends at the FAF. Last, the angle far exceeds 3 degrees, more like 10 degrees for a straight in.
GF
GF
Reposted from the VASI landing thread:
VERY important safety note: Non-precision RNAVs are being published showing a vertical Descent angle (VDA) and TCH on the approach chart. This information can be coded by avionics database providers to provide *advisory guidance* in the final segment. However, there is no TERPs criteria for obstacle clearance for the VISUAL segment of the path below the MDA. Consequetnly, if the VDA is blindly followed below MDA, an aircraft may come too close to, or impact obstacles or terrain penetrating the 34:1 surface extending out from the runway....
It is the pilot's responsibility to use the barometric altimeter to ensure compliance with altitude restrictions. Advisory vertical guidance is not approaved vertical guidance like that found on approaches with L/VNAV, LPV, ILS lines of minima. Advisory vertical guidance does not provide a TERPS-protected glidepath.
In short - BE CAREFUL!
It is the pilot's responsibility to use the barometric altimeter to ensure compliance with altitude restrictions. Advisory vertical guidance is not approaved vertical guidance like that found on approaches with L/VNAV, LPV, ILS lines of minima. Advisory vertical guidance does not provide a TERPS-protected glidepath.
In short - BE CAREFUL!
Last edited by USMCFLYR; 10-13-2012 at 02:34 PM.
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