NTSB Questions Civilian Risk in DC Plane Crash Hearing Due to Altimeter Discrepancies

Altimeter Discrepancies and Civilian Risk

• 🎯 NTSB member J. Todd Inman questioned witnesses about civilian risk stemming from discrepancies in aircraft altimeters, vital for measuring altitude.
• ⚠️ The hearing focused on a Jan. 29 collision between an Army helicopter and a regional jet that killed 67 people near Ronald Reagan National Airport.
• 💡 Witnesses explained that observed altimeter discrepancies are likely due to a "stack of the difference errors" involving device limitations and temperature effects, rather than maintenance issues.
• ✈️ These discrepancies are considered to be within the tolerance band for such errors, according to retired U.S. Army Colonel Steve Braddom.

Safety Tolerance and Separation Standards

• ❓ Inman pressed the panel on how much tolerance for aviation safety should exist when civilian lives are at risk, stating, "I think it should be zero."
• 📏 Army engineer Scott Rosengren expressed personal concern that the Federal Aviation Administration's requirement of at least 500 feet of separation between aircraft is insufficient given the known altimeter discrepancies.
• 📉 The discussion highlighted that physical limitations of altimeters can result in deviations of plus or minus 100 feet.
• 🤝 The NTSB member acknowledged the physical limitations of the machines providing the data, emphasizing the need to understand these constraints.

Aircraft Certification and Compliance

• 📜 Military aircraft flying in national airspace must undergo the same qualifications as commercial aircraft.
• ✅ While military aircraft comply with FAA requirements for flying in national airspace, they do not