Help with GPS (RNAV) approaches

This forum has been developed to discuss aviation related topics.

Moderators: ahramin, sky's the limit, sepia, Sulako, lilfssister, North Shore, I WAS Birddog

wan2fly99
Rank 4
Rank 4
Posts: 209
Joined: Tue Feb 17, 2004 12:04 pm

Help with GPS (RNAV) approaches

Post by wan2fly99 » Wed Dec 13, 2017 9:02 am

Getting back to flying again.
Everything is changing.
Localizer approaches, NDB approaches are going out the window. Home base in Oshawa CYOO now they have RNAV approaches instead of the localizer.

Can anybody point me to some good material I can read and get up to speed on all these approaches LP LNAV LNAV.VNAV

Its confussing
---------- ADS -----------
  

NotDirty!
Rank 4
Rank 4
Posts: 237
Joined: Wed May 21, 2014 4:04 pm

Re: Help with GPS (RNAV) approaches

Post by NotDirty! » Wed Dec 13, 2017 9:31 am

I believe what you are looking for is in the AIM, specifically COM 5.4.
Which minima you use is driven by the equipment you have available. Some GPSs can only do LNAV, while WAAS GPSs should be able to do LP and LPV approaches. I don't know of many GA GPSs that do LNAV/VNAV but not LPV, so you are most likely using either LNAV minima if you have an older GPS, or LPV minima if you have a newer GPS with WAAS and vertical guidance.

The actual mechanics of flying the approach is much simpler than your old NDB approaches, so that part should be pretty straight forward.
---------- ADS -----------
  

photofly
Top Poster
Top Poster
Posts: 7426
Joined: Tue Jan 18, 2011 4:47 pm
Location: Making aviation exhausting, everywhere

Re: Help with GPS (RNAV) approaches

Post by photofly » Wed Dec 13, 2017 9:36 am

You will also have to attend to the constant aescent angle on your non-precision approaches, for an instrument proficiency check. TC doesn't like the chop-and-drop any more.
---------- ADS -----------
  
Kirk: This is a dangerous mission. Likely, one of us will die. The landing party will be me, Spock, McCoy, and Ensign Ricky.
Ensign Ricky: Aw, crap.

AuxBatOn
Rank 11
Rank 11
Posts: 3080
Joined: Wed Jan 16, 2008 6:13 pm
Location: North America, sometimes

Re: Help with GPS (RNAV) approaches

Post by AuxBatOn » Wed Dec 13, 2017 10:22 am

Is this regulation or even guidance?
---------- ADS -----------
  
Going for the deck at corner

CpnCrunch
Rank 10
Rank 10
Posts: 2978
Joined: Mon Feb 08, 2010 9:38 am

Re: Help with GPS (RNAV) approaches

Post by CpnCrunch » Wed Dec 13, 2017 11:58 am

AuxBatOn wrote:
Wed Dec 13, 2017 10:22 am
Is this regulation or even guidance?
It says in the flight test guide:

"The use of step-down approach techniques where CDFA profiles are possible and practical will be considered a major error."

If you have WAAS, your GPS will likely show an advisory glideslope (LNAV+V) which you can use instead of the tables.
---------- ADS -----------
  

photofly
Top Poster
Top Poster
Posts: 7426
Joined: Tue Jan 18, 2011 4:47 pm
Location: Making aviation exhausting, everywhere

Re: Help with GPS (RNAV) approaches

Post by photofly » Wed Dec 13, 2017 1:39 pm

If you do have WAAS you can get the whole ride done at CYOO in about 0.6. Otherwise you'll have to go to Hamilton, Kitchener or (if you ask nicely) Trenton for the ILS.
---------- ADS -----------
  
Kirk: This is a dangerous mission. Likely, one of us will die. The landing party will be me, Spock, McCoy, and Ensign Ricky.
Ensign Ricky: Aw, crap.

CpnCrunch
Rank 10
Rank 10
Posts: 2978
Joined: Mon Feb 08, 2010 9:38 am

Re: Help with GPS (RNAV) approaches

Post by CpnCrunch » Wed Dec 13, 2017 2:23 pm

photofly wrote:
Wed Dec 13, 2017 1:39 pm
If you do have WAAS you can get the whole ride done at CYOO in about 0.6. Otherwise you'll have to go to Hamilton, Kitchener or (if you ask nicely) Trenton for the ILS.
I did hear an instructor saying recently that TC doesn't like this...they want you to do the precision and non-precision approaches at different airports.
---------- ADS -----------
  

photofly
Top Poster
Top Poster
Posts: 7426
Joined: Tue Jan 18, 2011 4:47 pm
Location: Making aviation exhausting, everywhere

Re: Help with GPS (RNAV) approaches

Post by photofly » Wed Dec 13, 2017 3:02 pm

It’s entirely possible that someone, somewhere, at TC has a hard on about it, and nobody else cares. I can only say that for several years I have been doing instrument rating tests and latterly instrument rating proficiency checks at CYHM - for both approaches and the hold. It has always been fine with my examiner.

I realize also that if the OP already holds a rating regardless of how long ago his recency lapsed, he doesn’t need to do a precision approach at all. So he could do an RNAV (LNAV) and an NDB approach, both at CYOO. I think.
---------- ADS -----------
  
Last edited by photofly on Wed Dec 13, 2017 3:06 pm, edited 1 time in total.
Kirk: This is a dangerous mission. Likely, one of us will die. The landing party will be me, Spock, McCoy, and Ensign Ricky.
Ensign Ricky: Aw, crap.

ahramin
Rank Moderator
Rank Moderator
Posts: 5835
Joined: Tue Feb 17, 2004 5:21 pm
Location: Vancouver

Re: Help with GPS (RNAV) approaches

Post by ahramin » Wed Dec 13, 2017 3:06 pm

CpnCrunch wrote:
Wed Dec 13, 2017 2:23 pm
photofly wrote:
Wed Dec 13, 2017 1:39 pm
If you do have WAAS you can get the whole ride done at CYOO in about 0.6. Otherwise you'll have to go to Hamilton, Kitchener or (if you ask nicely) Trenton for the ILS.
I did hear an instructor saying recently that TC doesn't like this...they want you to do the precision and non-precision approaches at different airports.
Every simulator PPC I have ever done all approaches were at the same airport. I would question the instructor on where this idea came from.
---------- ADS -----------
  

AuxBatOn
Rank 11
Rank 11
Posts: 3080
Joined: Wed Jan 16, 2008 6:13 pm
Location: North America, sometimes

Re: Help with GPS (RNAV) approaches

Post by AuxBatOn » Wed Dec 13, 2017 3:25 pm

CpnCrunch wrote:
Wed Dec 13, 2017 11:58 am
AuxBatOn wrote:
Wed Dec 13, 2017 10:22 am
Is this regulation or even guidance?
It says in the flight test guide:

"The use of step-down approach techniques where CDFA profiles are possible and practical will be considered a major error."

If you have WAAS, your GPS will likely show an advisory glideslope (LNAV+V) which you can use instead of the tables.
The Flight Test Guide should be supported by regulaion or guidance. The Flight Test Guide is not regulation nor guidance from an operations POV. Nothing in the rules say I should not conduct step downs during a NPA.
---------- ADS -----------
  
Going for the deck at corner

cap41
Rank 4
Rank 4
Posts: 271
Joined: Thu Oct 04, 2012 7:36 pm
Location: Oshawa (CYOO)

Re: Help with GPS (RNAV) approaches

Post by cap41 » Wed Dec 13, 2017 4:03 pm

I think the NDB at CYOO was decommissioned last year.
---------- ADS -----------
  

photofly
Top Poster
Top Poster
Posts: 7426
Joined: Tue Jan 18, 2011 4:47 pm
Location: Making aviation exhausting, everywhere

Re: Help with GPS (RNAV) approaches

Post by photofly » Wed Dec 13, 2017 4:14 pm

AuxBatOn wrote:
Wed Dec 13, 2017 3:25 pm
CpnCrunch wrote:
Wed Dec 13, 2017 11:58 am
AuxBatOn wrote:
Wed Dec 13, 2017 10:22 am
Is this regulation or even guidance?
It says in the flight test guide:

"The use of step-down approach techniques where CDFA profiles are possible and practical will be considered a major error."

If you have WAAS, your GPS will likely show an advisory glideslope (LNAV+V) which you can use instead of the tables.
The Flight Test Guide should be supported by regulaion or guidance. The Flight Test Guide is not regulation nor guidance from an operations POV. Nothing in the rules say I should not conduct step downs during a NPA.
This thread isn’t about you or how you fly :-). It’s about someone who is going to need to pass an instrument proficiency test while flying RNAV and/or other non precision approaches. if he or she wants to pass that test it makes sense for them to follow the requirements of the flight test guide. Some flight tests have restrictions and requirements that go beyond the regulations. This is one such case.
cap41 wrote:
Wed Dec 13, 2017 4:03 pm
I think the NDB at CYOO was decommissioned last year.
It’s still there, and there’s still an approach based on it: NDB RWY05. Two, if you count the NDB/DME RWY05 as separate.

Both plates are valid until 1FEB 2018, so nobody is planning on decommissioning the beacon at least till then.
---------- ADS -----------
  
Kirk: This is a dangerous mission. Likely, one of us will die. The landing party will be me, Spock, McCoy, and Ensign Ricky.
Ensign Ricky: Aw, crap.

ahramin
Rank Moderator
Rank Moderator
Posts: 5835
Joined: Tue Feb 17, 2004 5:21 pm
Location: Vancouver

Re: Help with GPS (RNAV) approaches

Post by ahramin » Wed Dec 13, 2017 6:52 pm

AuxBatOn makes a good point. Let's say you fail an IFR flight and one of the 2s that lead to that failure was a dive and drive NPA. Shouldn't you be able to ask the examiner to defend that mark with more than just the flight test guide? Is there some other document that the examiner can point to? Or is it the same as the requirements to meet stay within certain limits of speed and altitude targets?
---------- ADS -----------
  

photofly
Top Poster
Top Poster
Posts: 7426
Joined: Tue Jan 18, 2011 4:47 pm
Location: Making aviation exhausting, everywhere

Re: Help with GPS (RNAV) approaches

Post by photofly » Wed Dec 13, 2017 7:05 pm

I’m fairly sure the examiner is required to abide by the flight test guide. On the basis of consistency, if nothing else. Kind of above his or her pay grade to go against it, as an extremely junior delegatee of the minister’s responsibility to issue licences and ratings.

Could you appeal to TC? Probably. Id love to hear the argument, but totally not worth it in time or money. Just fly the approach like they ask. It’s not difficult.
---------- ADS -----------
  
Kirk: This is a dangerous mission. Likely, one of us will die. The landing party will be me, Spock, McCoy, and Ensign Ricky.
Ensign Ricky: Aw, crap.

AuxBatOn
Rank 11
Rank 11
Posts: 3080
Joined: Wed Jan 16, 2008 6:13 pm
Location: North America, sometimes

Re: Help with GPS (RNAV) approaches

Post by AuxBatOn » Wed Dec 13, 2017 8:11 pm

photofly,

Standards of a test flight cannot be made out of thin air. They need to be substianted otherwise, it is unenforceable. You should only be evaluated on things that are published as regulation or official guidance. It's not about whether the examiner has to abide by the guide or not. It's about whether the guide is right or not.
---------- ADS -----------
  
Going for the deck at corner

photofly
Top Poster
Top Poster
Posts: 7426
Joined: Tue Jan 18, 2011 4:47 pm
Location: Making aviation exhausting, everywhere

Re: Help with GPS (RNAV) approaches

Post by photofly » Wed Dec 13, 2017 8:17 pm

I don’t agree. Of course flight test standards are invented, if not out of thin air then by people who feel they know something about the subject. Show me the official guidance or regulation outside of the relevant flight test guide for a PPL to meet +/- 100’ altitude tolerance during a steep turn, or +/- 200’ during cross country navigation.

I think the penchant for CDA approaches comes from some research about safety during non precision approaches. Not sure where I heard that. But for sure they didn’t make it up without discussion on a dreary wednesday morning for a laugh.

You might not agree with whether it’s a preferred way to fly an approach, but TC has the right to test whatever they want to test and think is important. This is testing, after all, and not enforcement.
---------- ADS -----------
  
Kirk: This is a dangerous mission. Likely, one of us will die. The landing party will be me, Spock, McCoy, and Ensign Ricky.
Ensign Ricky: Aw, crap.

User avatar
confusedalot
Rank 8
Rank 8
Posts: 910
Joined: Fri Jul 03, 2009 9:08 pm
Location: location, location, is what matters

Re: Help with GPS (RNAV) approaches

Post by confusedalot » Wed Dec 13, 2017 8:26 pm

The OP asked for training purpose information, not flight test requirements.

I would like to help you but this message would be very very long. As a start, google GPS, RAIM, WAAS, LNAV/VNAV, LPV. Also, much of the input and output will be dependent on which GPS equipment you are using, so have a read in you particular manual. No point in telling you what I did in a smith's or Honeywell FMS unless that is what you have.

Also, you don't need WAAS sensors to do LNAV/VNAV limits, you will get vertical guidance without it but you cannot use LPV minima without WAAS.
---------- ADS -----------
  
Attempting to understand the world. I have not succeeded.

veni, vidi,...... vici non fecit.

:?

Aviatard
Rank 6
Rank 6
Posts: 422
Joined: Fri Aug 05, 2005 2:45 am
Location: In a box behind Walmart

Re: Help with GPS (RNAV) approaches

Post by Aviatard » Thu Dec 14, 2017 3:58 am

AuxBatOn wrote:
Wed Dec 13, 2017 3:25 pm

The Flight Test Guide should be supported by regulaion or guidance. The Flight Test Guide is not regulation nor guidance from an operations POV. Nothing in the rules say I should not conduct step downs during a NPA.
421.17 Failure of a Flight Test for a Rating Renewal

(1) The Flight Test Requirements to determine whether an applicant passes, meets a lower class of that rating or fails the renewal flight test for the rating are found in the applicable Flight Test Standards and Guides.
---------- ADS -----------
  

wan2fly99
Rank 4
Rank 4
Posts: 209
Joined: Tue Feb 17, 2004 12:04 pm

Re: Help with GPS (RNAV) approaches

Post by wan2fly99 » Thu Dec 14, 2017 6:56 am

Thanks everybody. Got to start googling now.

Just not sure what the difference is between LP and LNAV.

Also LNAV/VNAN go to start reading
---------- ADS -----------
  

photofly
Top Poster
Top Poster
Posts: 7426
Joined: Tue Jan 18, 2011 4:47 pm
Location: Making aviation exhausting, everywhere

Re: Help with GPS (RNAV) approaches

Post by photofly » Thu Dec 14, 2017 7:18 am

LP : recent invention by the FAA. Stands for localizer performance.

LNAV approaches have a protected area that’s a funny complicated shape of rectangles and triangles narrowing towards the runway, and the receiver sequences through three different fixed sensitivities (5nm deviation full scale deflection, then 1nm, then 0.3nm) at set points in the approach. The daddy of GPS approach design, they’ve been around for decades.

LP approaches have a simpler protected area, and the needle full scale deflection is based on angular deviation from the centreline, continuously getting more sensitive the closer you are, just like a localizer approach.

In a few cases because of the smaller protected area an LP approach can have (slightly) lower minima than an LPV approach. It’s still not a precision approach and any vertical guidance provided by the GPS receiver is advisory only.

Finally, since they’re new, only very recent GPS units are capable of LP approaches.

LNAV/VNAV is a capability of larger aircraft without WAAS whose FMS can integrate other altitude information with GPS data to get reliable approaches to lower minima than GPS alone. i don’t believe they have much relevance for small aircraft: you either have WAAS in which case you can use LPV minima, or you don’t, in which case you must use LNAV minima.
---------- ADS -----------
  
Kirk: This is a dangerous mission. Likely, one of us will die. The landing party will be me, Spock, McCoy, and Ensign Ricky.
Ensign Ricky: Aw, crap.

User avatar
confusedalot
Rank 8
Rank 8
Posts: 910
Joined: Fri Jul 03, 2009 9:08 pm
Location: location, location, is what matters

Re: Help with GPS (RNAV) approaches

Post by confusedalot » Thu Dec 14, 2017 6:37 pm

I guess that I have been spoiled by good equipment, so here is my question out of curiosity.

Could some types of general aviation GPS enroute and non precision approach certified equipment also have vertical (VNAV) guidance that would suffice without having a WAAS platform? it would sure save alot of grief of looking at those CDA constant descent angle charts.

I flew a bizjet for ahwile with a universal fms and it seems to me that it had it, but that was a while ago and my memories of it are fuzzy.
---------- ADS -----------
  
Attempting to understand the world. I have not succeeded.

veni, vidi,...... vici non fecit.

:?

photofly
Top Poster
Top Poster
Posts: 7426
Joined: Tue Jan 18, 2011 4:47 pm
Location: Making aviation exhausting, everywhere

Re: Help with GPS (RNAV) approaches

Post by photofly » Thu Dec 14, 2017 7:42 pm

I have tried several times to find a definitive answer to that, and failed.

I have an older GPS, non-WAAS, that gets a barometric altitude from the transponder encoder to improve RAIM availability. Even though it has that, it doesn’t qualify for LNAV/VNAV.

There is a TC document that goes into fearsome detail what kind of equipment and paperwork is required for an OC holder to conduct LNAV/VNAV approaches but it doesn’t say what a privately registered aircraft would need.
---------- ADS -----------
  
Kirk: This is a dangerous mission. Likely, one of us will die. The landing party will be me, Spock, McCoy, and Ensign Ricky.
Ensign Ricky: Aw, crap.

AuxBatOn
Rank 11
Rank 11
Posts: 3080
Joined: Wed Jan 16, 2008 6:13 pm
Location: North America, sometimes

Re: Help with GPS (RNAV) approaches

Post by AuxBatOn » Thu Dec 14, 2017 9:12 pm

How does baro altitude help with RAIM availability?!
---------- ADS -----------
  
Going for the deck at corner

photofly
Top Poster
Top Poster
Posts: 7426
Joined: Tue Jan 18, 2011 4:47 pm
Location: Making aviation exhausting, everywhere

Re: Help with GPS (RNAV) approaches

Post by photofly » Fri Dec 15, 2017 6:03 am

It reduces the number of satellites required to be in view:

https://www.faa.gov/about/office_org/he ... FSheet.pdf
“Barometric Aiding (Baro-Aiding)
Barometric aiding is an integrity augmentation that allows a GPS system to use a non-satellite input source (e.g. the aircraft pitot-static system) to provide vertical reference and reduces the number of required satellites from five to four. Baro-aiding requires four satellites and a barometric altimeter input to detect an integrity anomaly. The current altimeter setting may need to be entered into the receiver as described in the operating manual. Baro-aiding satisfies the Receiver Autonomous Integrity Monitoring (RAIM) requirement in lieu of a fifth satellite.”

My GPS receiver AFMS says much the same thing, and the unit does indeed require the altimeter setting to be entered prior to commencing an approach.

Note: that FAA document answers some of the other questions posed in this thread, too. The OP should read it.
---------- ADS -----------
  
Kirk: This is a dangerous mission. Likely, one of us will die. The landing party will be me, Spock, McCoy, and Ensign Ricky.
Ensign Ricky: Aw, crap.

Cessna 180
Rank 4
Rank 4
Posts: 263
Joined: Wed Sep 23, 2015 8:28 pm
Location: YKF

Re: Help with GPS (RNAV) approaches

Post by Cessna 180 » Fri Dec 15, 2017 11:52 am

AuxBatOn wrote:
Thu Dec 14, 2017 9:12 pm
How does baro altitude help with RAIM availability?!
I believe the GPS unit needs VNAV ability? I've used VNAV before on older G1000 installations without WAAS (never for an approach however) and I believe this would qualify for an LNAV/VNAV approach. I've also done multiple LNAV/VNAV approaches using non-wass FMS 3000 approaches on older Pro Line 21 King Airs and its similar to the way you shoot an approach on the G1000.
---------- ADS -----------
  

Post Reply

Return to “General Comments”