The abbreviated version up front: vectoring and approach clearances are routine tools for ATC, but they do not relieve the pilot of responsibility for meeting published approach minimums or for rejecting an unstable approach. The preliminary NTSB data for the Citation S550 known as N666DS shows a textbook chain of factors that can convert a routine RNAV clearance into a catastrophic outcome when crew workload, night IMC, inoperative airport equipment, and marginal weather converge.

What the data shows, in operational terms

  • The crew was cleared for the RNAV (GPS) runway 28R procedure into Montgomery-Gibbs and flew a profile that was aligned laterally with the procedure but descended below published step-down/ crossing altitudes as they proceeded inbound. ADS-B and the NTSB preliminary reconstruction show the airplane crossing a published waypoint significantly below its published minimum altitude and subsequently striking high-voltage transmission lines located on the approach path.

  • The approach environment was degraded. The airport automated weather source was out of service and the pilot attempted to use pilot-controlled lighting, increasing cockpit workload in low-visibility night conditions. The pilot had a single-pilot exemption for that airframe. These are the ingredients that tend to erode margins quickly: higher workload, limited outside visual cues, and fewer crewmembers to distribute tasks.

  • Public reporting and ADS-B analysis indicate controllers provided nearby weather but did not provide a recorded altimeter setting on the approach frequency, which investigators flagged as a likely area of focus. Pilots cannot assume an altimeter setting; they must request and set one when flying an instrument approach at night in marginal visibility.

Why vectoring and clearances are not automatic safety net Controllers clear and vector aircraft to sequence traffic, avoid weather, or establish aircraft on an approach. A clearance to fly an RNAV approach establishes lateral and procedural responsibilities, but it does not shift final lateral and vertical responsibility away from the pilot. The pilot must: brief the exact approach variant (LPV vs LNAV), confirm minimums and crossing altitudes, set the correct altimeter, confirm lighting status/requirements, and fly a stabilized approach or go missed. The NTSB preliminary material for N666DS shows a lateral track consistent with the RNAV procedure but vertical deviation below the published minima. That combination is what produces wirestrike or obstacle strikes on final.

Practical items pilots flying bizjets into urban airports should lock in before committing to an approach

  • Confirm the approach variant. RNAV GPS approaches often have LPV and LNAV minima with different vertical guidance and minimums. Decide and brief which you will fly. If you accept an RNAV clearance without specifying LPV or LNAV, clarify it early.
  • Get an altimeter setting. If the destination ASOS/AWOS is out, get the nearest reliable setting and cross-check. Do not fly a night IMC approach without a confirmed pressure setting.
  • Stabilized approach discipline. By final approach the aircraft should be on the lateral and vertical path, configured, and at a safe airspeed. If you are not stabilized, go around. That is non-negotiable in urban approaches where obstacles and transmission lines can be close to the final path.
  • Resist ‘we will be alright’ mentality. Heavy jets and light bizjets have different energy and handling characteristics at night. If workload is spiking, declare inability and request vectors or diversion. ATC can vector you, but they cannot fly the plane for you.
  • Single-pilot risk management. If you are operating single pilot in complex, long-leg night IMC conditions, plan more conservative margins: higher stabilized approach minima, earlier diversion decisions, and use of autopilot/flight director vertical guidance when available. The NTSB documents note the pilot was operating under an exemption to fly the airframe single-pilot. That fact places a premium on conservative decision making.

What ATC and airports can do to reduce urban exposure

  • Proactive altimeter practice. When tower or approach knows the destination ASOS is out, a standard phraseology reminder to provide an altimeter setting for approach work saves time and confusion. Public reporting indicates the controller provided weather from a nearby station but an altimeter setting was not recorded on the approach frequency; making that explicit should be standard practice.
  • Charted obstacle awareness. Where transmission lines or other obstacles penetrate approach surfaces, working with airport operators and utilities to highlight those threats on approach charts, briefings, and NOTAMs helps crews plan more margin. The NTSB preliminary data tied the first point of contact to power lines that cross the approach path. That is exactly the kind of locally significant hazard that benefits from repeated emphasis.
  • Community and noise interface. Urban airports already operate with tight community noise constraints. San Diego area airports track noise and flight paths for civilian concerns. Transparent coordination between noise abatement procedures and safety-critical minima is essential so pilots are not put in the position of choosing community-friendly tracks over safety buffers.

Bottom line for flying professionals Vectoring and ATC clearances are indispensable for efficient flow, but they are not a substitute for sound approach discipline. When you combine night, marginal weather, an out-of-service AWOS, single-pilot operations, and complex RNAV variants, you must tighten your personal minima and be prepared to ask for vectors, hold, or divert. The preliminary NTSB record for N666DS is a sober reminder that lateral alignment without vertical discipline over urban terrain is a fragile condition. Fly the profile, fly the minima, go missed early when things are not stable, and brief where obstacles and lighting considerations can change the game on final.