Unknown type · N550DR
Altitude profile · flown vs. floor
Plan view · the three areas & the track flown
What happened
On a arrival from Hong Kong International Airport (HKG), N550DR crossed into the noise-abatement area over Yishun (Area 1), where the published floor is 1,500 ft, and descended to a QNH-corrected 645 ft — 855 ft below the floor.
In-area minimum
645 ft corrected, over Yishun.
Rule
Yishun · 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 1010 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 855 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 →