Aircraft which have been in service for a long time often have a lot of entries in their logbooks for Airworthiness Directives (ADs). What are they, and why are they important?
Airworthiness Directives (ADs) are legally enforceable rules issued by the FAA in accordance with 14 CFR part 39 to correct an unsafe condition in a product. 14 CFR part 39 defines a product as an aircraft, aircraft engine, propeller, or appliance.
When an aircraft or other component is found to have flaws or other issues, the FAA will issue an AD specifying a solution to be applied to the item. The AD must be complied with, often by a date or total time on the airframe. The action required could simply be an inspection (often recurring after, say, 100 hours of time in service), while in other cases requires modification, strengthening, or replacement of parts.
One of the more prominent cases requiring ADs to be issued was the V-tail Bonanza, which had issues with the tail's structural integrity under high loads.
The cost of complying with an AD falls on the owner/operator of the aircraft. Failing to comply with an AD renders the aircraft unairworthy. It also could incur FAA penalties, but more importantly, it could result in structural damage or failure, and in some cases ultimately cause a fatal accident.
What are cowl flaps and what are they used for? It seems I have only heard of them in connection with old planes, are they peculiar to radial engines?
Some aircraft have pusher type propellers. In what ways is it different from a tractor type propeller? What's are the advantages and disadvantages over a tractor type.
It has been suggested in the media and in some answers here that airlines vary in the information they track about the status of their flights. Is there a publicly available resource that lists what information different airlines have about the location and status of their flights? For example, could a British Airways flight over the Atlantic or the middle of the Pacific have "vanished" in the same way that the Malaysian flight over the Gulf of Thailand?
In remote areas that have no radar (oceanic airspace, etc.) how is aircraft separation maintained so that airplanes don't get too close? What do areas that normally have radar do when there is a sudden radar outage? There are airplanes going everywhere, not necessarily on standard airways, and a lot of them are being given radar vectors. What happens when the screens go dark?
When the transponder on Malaysia Airlines Flight 370 went off, there was no ALARM. The satellite kept getting pings, and apparently "knew" that the transponder was off. Would it not be a great idea if the Malaysia Airlines got an alarm indication that the transponder was off on one of their planes? The airline could have radioed the pilot and asked what the trouble was. If the pilots did not respond, some jets could have been scrambled to checkout what is going on. The scrambled jets could have followed the airliner for hours and watched them crash in the ocean, when they ran out of fuel. We
According to Airbus: ‐ After the flight crew selects reverse thrust, they must perform a full stop landing. Does it really make sense to have this limitation, and why? What happens if you realise there's not enough space to land, and you've still got adequate speed?
Large passenger planes almost always have their engines hanging from the wings, Fighters usually have them in the rear, and small Cessnas have them on the nose. What is the reason for these variations in design?
I have heard that some aircraft that do not have an APU can run an engine in "Hotel Mode". What is hotel mode? Are there any advantages to having it instead of an APU?
What would be the most optimal shape for a quadcopter design? I have tried the cross beam design, but the center joint, though epoxied, is extremely prone to shearing off on impact.
Last August during a certification flight, a Cessna 182JT-A compression-ignition (diesel) engine failed in flight. I've been Googling to find the cause of the failure and the status of the certification process but have failed to find any recent info. Does anyone know what the current findings have been and how Cessna expects to proceed?