Corporate jet captain reported observing a near-collision between a gulfstream landing on hpn runway...

Narrative:

Hpn airport; holding short of runway 34; awaiting takeoff clearance; the crew observed the following. A gulfstream was cleared to land runway 34. The gulfstream was in the landing flare at approximately 40 feet when tower issued 'go around; go around' to the gulfstream. We were watching it land when the command was issued. The gulfstream pitched up and executed a go around as a small cessna landing runway 29 passed directly under the gulfstream on the landing rollout. I estimate 50 feet separation; at most. We observed this from about 150 yards away. This was about as close as it gets without an explosion. The gulfstream returned for a landing and ask 'why the go-around'. Tower replied; cessna landed without landing clearance. Nothing else was said between tower and the gulfstream. I believe tower/ATC/approach made a near fatal error in not recognizing the proximity of the cessna to the cleared to land gulfstream. After the event; operations resumed normally with business jets/airliners landing 34 and small aircraft landing one after another runway 29. I believe during these type of operations a high level of vigilance should exist between only highly experienced tower/ATC controllers. I have seen similar incidents happen at hpn. Tower controller seemingly [had] 'lack of experience' or [experienced] 'loss of situational awareness.'

Original NASA ASRS Text

Title: Corporate jet Captain reported observing a near-collision between a Gulfstream landing on HPN Runway 34 and a Cessna landing on Runway 29. Reporter was of the opinion it was an ATC error.

Narrative: HPN airport; holding short of Runway 34; awaiting takeoff clearance; the crew observed the following. A Gulfstream was cleared to land runway 34. The Gulfstream was in the landing flare at approximately 40 feet when tower issued 'go around; go around' to the Gulfstream. We were watching it land when the command was issued. The Gulfstream pitched up and executed a go around as a small Cessna landing runway 29 passed directly under the Gulfstream on the landing rollout. I estimate 50 feet separation; at most. We observed this from about 150 yards away. This was about as close as it gets without an explosion. The Gulfstream returned for a landing and ask 'why the go-around'. Tower replied; Cessna landed without landing clearance. Nothing else was said between Tower and the Gulfstream. I believe Tower/ATC/Approach made a near fatal error in not recognizing the proximity of the Cessna to the cleared to land Gulfstream. After the event; operations resumed normally with business jets/airliners landing 34 and small aircraft landing one after another Runway 29. I believe during these type of operations a high level of vigilance should exist between only highly experienced Tower/ATC Controllers. I have seen similar incidents happen at HPN. Tower controller seemingly [had] 'lack of experience' or [experienced] 'loss of situational awareness.'

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1418691
Time
Date	201701
Local Time Of Day	1201-1800
Place
Locale Reference	HPN.Airport
State Reference	NY
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Light Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 91
Flight Phase	Taxi
Flight Plan	IFR
Aircraft 2
Make Model Name	Gulfstream Jet Undifferentiated or Other Model
Flight Phase	Landing
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	ATC Issue All Types Conflict Ground Conflict Critical

Corporate jet captain reported observing a near-collision between a gulfstream landing on hpn runway 34 and a cessna landing on runway 29. Reporter was of the opinion it was an ATC error.