Unknown type · N899ST
Altitude profile · flown vs. floor
Plan view · the three areas & the track flown
What happened
On a arrival from Hong Kong International Airport (HKG), N899ST crossed into the noise-abatement area over Yio Chu Kang (Area 2), where the published floor is 1,500 ft, and descended to a QNH-corrected 731 ft — 769 ft below the floor.
In-area minimum
731 ft corrected, over Yio Chu Kang.
Rule
Yio Chu Kang · 1,500 ft floor. A hard performance gate — no landing exemption.
Why these altitudes are trustworthy
ADS-B broadcasts pressure altitude against a standard datum. We re-reference every value to the QNH of 1007 hPa — the altimeter setting this aircraft itself broadcast near Seletar — so the figures are what the pilot read on the altimeter.
How sure we are
The 769 ft gap is well beyond the combined ADS-B + QNH measurement margin, so the aircraft was below the minimum beyond any measurement doubt — this is asserted, not provisional. Readings within the margin are held back and never published here.
What we can't see. Public data does not show an ATC descent clearance or rule out a genuine emergency. There is no landing exemption here, and medical-evacuation status — a curfew-only exemption — does not apply to the noise-abatement floors. We publish the measurement and the caveat together. Flew a medevac, diversion or emergency, or spotted an error? Declare an exemption or correction →