387 Vectors to Final and glide path behavior on RNAV (GPS) approaches + GA News

Max talks about common gotchas with RNAV GPS approaches, especially when using vectors to final (VTF). The conversation picks up where Episode 383 left off, with listeners asking how vectors to final (VTF) influences glidepath capture on WAAS approaches.

He explains that under normal circumstances—flying the approach via own navigation from an initial approach fix (IAF)—the GPS glidepath doesn’t turn magenta or allow autopilot coupling until the FAF becomes the active waypoint. The magenta color indicates that the GPS receiver has completed a signal quality evaluation, verifying that the WAAS signal is good enough for LPV minimums. Until this point, the glidepath indicator remains a hollow white diamond, and the autopilot will not descend.

However, activating VTF triggers this signal check immediately, regardless of the aircraft’s location. If the aircraft’s track is within approximately 100–110° of the final approach course, the glidepath indicator turns magenta and autopilot coupling becomes possible—even miles from the airport. This can be risky if the aircraft is outside the protected segment of the published procedure, especially in mountainous terrain where blindly following the glidepath can be hazardous.

Max notes that activating VTF early, particularly from a downwind leg, may display the “SUSP” annunciator. He urges pilots not to press the SUSP button in this scenario, as it can inadvertently sequence legs inappropriately or disable the approach altogether. The SUSP annunciator will clear automatically during the final base-to-final turn, provided it's within 45° of the final approach course.

The episode then shifts to a common gotcha with ILS and RNAV approaches when being vectored in close. If a controller brings an aircraft in at an altitude that puts it above the glidepath—and the vertical deviation indicator centers before the lateral CDI centers—the autopilot will capture lateral guidance but not vertical guidance. Max describes this firsthand from a recent Vision Jet flight into Orange County, where his awareness helped avoid a missed capture. If the autopilot fails to capture the glidepath due to this timing issue, pilots must use vertical speed (VS) mode to manually descend and re-intercept it.

Responding to listener Matt’s question, Max discusses the use of VNAV (Vertical Navigation) mode as another way to descend to the glidepath for early coupling. He clarifies that while VNAV is a separate topic, it’s related because it can assist with managing step-down altitudes more precisely. If VNAV is properly configured—usually in conjunction with the APPR key—it can manage the descent and transition into the glidepath at the FAF. However, Max warns of several pitfalls: pilots often forget to dial in a lower altitude, which prevents descent; older G1000 systems may ignore VNAV commands if the top of descent (TOD) is more than five minutes away; and using VNAV may not align with ATC altitude restrictions.

He concludes that while VNAV has become more reliable due to Garmin software improvements, it introduces complexity and requires careful verification of ATC clearances and altitude settings.

If you're getting value from this show, please support the show via PayPal, Venmo, Zelle or Patreon.

Support the Show by buying a Lightspeed ANR Headsets
Max has been using only Lightspeed headsets for nearly 25 years! I love their tradeup program that let's you trade in an older Lightspeed headset for a newer model. Start with one of the links below, and Lightspeed will pay a referral fee to support Aviation News Talk.
Lightspeed Delta Zulu Headset $1199
Lightspeed Zulu 3 Headset $899
Lightspeed Sierra Headset $699
My Review on the Lightspeed Delta Zulu

Send us your feedback or comments via email

If you have a question you’d like answered on the show, let listeners hear you ask the question, by recording your listener question using your phone.

News Stories

• DOT Begins Search for Lead Contractor in ATC Overhaul
• GAMI G100UL not universal enough to replace avgas in California
• Beta Makes First Electric Flight into New York's JFK Airport
• Spatial disorientation: GA’s deadliest threat
• Model injured during photo shoot with Aviat pilot
• Pilot loses control on landing when feet get stuck on rudder
• North Pole man accused of flying while intoxicated

Mentioned on the Show
Buy Max Trescott's G3000 Book Call 800-247-6553
Lightspeed Delta Zulu Headset Giveaway
Video of the Week: Canopies Open during A-26 Intruder Flight 
NTSB News Talk Podcast
UAV News Talk Podcast
Rotary Wing Show Podcast

Free Index to the first 282 episodes of Aviation New Talk

So You Want To Learn to Fly or Buy a Cirrus seminars
Online Version of the Seminar Coming Soon – Register for Notification

Check out our recommended ADS-B receivers, and order one for yourself. Yes, we’ll make a couple of dollars if you do.

Get the Free Aviation News Talk app for iOS or Android.

Check out Max’s Online Courses: G1000 VFR, G1000 IFR, and Flying WAAS & GPS Approaches. Find them all at: https://www.pilotlearning.com/

Social Media
Like Aviation News Talk podcast on Facebook
Follow Max on Instagram
Follow Max on Twitter
Listen to all Aviation News Talk podcasts on YouTube or YouTube Premium

"Go Around" song used by permission of Ken Dravis; you can buy his music at kendravis.com

If you purchase a product through a link on our site, we may receive compensation.