Light Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 30; Flight Crew Total 6100; Flight Crew Type 1512
Communication Breakdown; Situational Awareness; Confusion; Human-Machine Interface
ATC Issue All Types; Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew FLC Overrode Automation
Aircraft; Chart Or Publication; Human Factors; Procedure
MDW was using one of the new RNAV GPS approaches; RNAV (GPS) Z Runway 22L. No problem; we have a relatively new Universal 1FW with WAAS. Loaded up the approach and noticed that even though the approach seemed to load normally with all of the waypoints and banners; needed for the approach; once loaded it did not show that an approach was loaded into the FMS on the NAV page 1. I was not able to arm or activate it--as would be correct since the FMS was not showing the approach as loaded on the NAV page; yet there it was in all of its glory on the FLTPLAN page. Since it was VFR we ended up being assigned traffic to follow and it became a non-event. When we returned to our home base I contacted the FMS manufacturer and spoke to our trainer. I asked him why it would not work and I ended up performing a maintenance download. We have a dual FMS installation and both were operating identically. Upon further questioning it was determined that the approach we were trying to do was an LP [Localizer Performance (without Vertical Guidance)] approach although we were not aware of this. After doing more research we discovered that even though our FMS is WAAS certified; this particular approach came out after it was certified. Universal did not want to do the paperwork to recertify it for these approaches; but included them in the database and labeled them with an (a) [appended to the left of the approach designator in the FMS 'list of approaches']. I discovered this on one of my many calls with our trainer discussing this issue after the event. These are labeled with the (a) [to denote them] as an advisory or advanced approach. This [status allows selection and display] of everything in there but we are unable to arm and activate it. Our FMS is not certified for these LP approaches although it is WAAS certified for LPV approaches. Since it is LPV WAAS certified it has this approach in the database. Interestingly; I contacted a flight test pilot that I know with [another FMS manufacturer] and their avionics systems do the same thing.Big problem is the approach chart. I thought; through some research on LP approaches; they were supposed to have 'LP' in their [title]; but they do not. It just says RNAV (GPS) Z Runway 22L. Only in the minimums sections do you discover that there is something different about this. Also; you just can't revert back to an LNAV approach even though it is listed as such on the approach plate because we still don't have any guidance or approach criteria from the FMS! Now this is a dilemma as we were lucky enough to discover [the problem] while we were VFR but I certainly wouldn't have wanted to find this out IFR amongst the tall buildings in Chicago and I'll bet in the future when we have to decline this approach we won't be ATC's best friend. This is a big problem as there are some 500 of these approaches out there waiting to bite the unsuspecting aviator who thinks that their WAAS GPS will fly anything. Something needs to be done to get the word out as I raised a huge red flag with Universal and maybe with Rockwell but now that these approaches are there and the WAAS GPSs can fly them; maybe yes and maybe no and there is no reversion to LNAV for those that can't but still have a WAAS GPS. At least I know what to look for on the RNAV approach plates; so I won't fall into this trap; but I'll bet that there are quite a few [pilots] that don't.How is that for a gotcha!
The reporter advised that his subsequent investigations indicate that problems unique to at least some of the LP approaches is that they are utilized on offset lateral guidance approaches with obstacle clearance issues as in the case of the MDW RNAV LP to 22L where the inbound course is offset 10 degrees from the extended runway centerline due to downtown Chicago high rises. The analyst determined this is not always the case as other LP approaches are conducted on the extended centerline such as at DAB RNAV (GPS) Runway 34 approach. Reporter believed this offset criteria impacted his operation because the aircraft's FMS requires that the autoflight approach mode be selected to activate mode annunciation lights and allow approach guidance. He did not know if that specification/limitation is common to all LP approaches and/or aircraft.He further stated that operators of his aircraft would have no obvious means of determining their performance capability shortfall until attempting to arm the approach mode to fly an LP approach and; only then late in the arrival; discovering approach mode functions not available.He feels strongly that any approaches/procedures that are not capable of being utilized by a given aircraft's flight crew should NOT be in the database and most especially should not be line selectable thus predisposing unsuspecting crews to the assumption of their expected normal operation. He stressed that the lack of an 'LP' in the approach title adds to the difficulty of determining what useable approaches are available; requiring that each individual approach minimums displays be reviewed to weed out the chaff.Finally; he stressed that it is his understanding that the decision to not recertify FMS systems to provide LP capability is not unique to the manufacturer of the system in his aircraft. He has received no notification from his company; the FMS manufacturer or the FAA alerting him to the dysfunctional nature of data available to him and; perhaps; other users.
A corporate jet flight crew cleared to fly the RNAV (GPS) 22L approach to MDW discovered that; although the approach was in their FMS database and could be loaded it could not be executed and utilized to fly the approach. The flight was in VMC and continued the approach landing uneventfully. Subsequent inquiries determined the approach utilized LP (Localizer Performance) minimums and that; although present in the database; had not been certified for use by the manufacturer due to their late availability just after the hardware/software itself had been certified.