Flying below the MEA: when the MEAs over mountains stretch into the oxygen altitudes, you might sneak past a bit lower, but it's probably not kosher.
A few readers asked how this request could be legal. The short answer is, it isn't exactly legal, but sometimes it works.
FAR 91.179, "IFR Cruising Altitude or Flight Level," states that, in controlled airspace, you must fly the altitude assigned by ATC unless you're operating VFR-on-top. VFR-on-top aircraft fly the "plus-500" altitudes of their choosing, but they are still on IFR flight plans, so FAR 91.177, "Minimum altitudes for IFR operations," applies. This says that, except when necessary for takeoff or landing, you must fly the published altitudes, or 2000 feet over the big rocks and 1000 feet over the hills and flatlands where no published altitude exists.
It also specifically says you can only go below the MEA within 22 miles of the VOR defining a route. Even then, you can't go below the Minimum Obstacle Clearance Altitude (MOCA).
The controller's bible 7110.65 contains some strict language on this, too. Paragraph 4-5-6 states that the controller can clear aircraft below the MEA but not below the MOCA (Minimum Obstacle Clearance Altitude) for the route segment being flown if the altitude is at least 300 feet above the floor of controlled airspace. On routes without MEAs the controller cannot clear an aircraft below the altitudes prescribed by FAR 91.177. Also, the flight must be in radar contact and the request must be of "operational advantage." Presumably, your getting a better altitude while not messing up the controller's day qualifies.
So perhaps you could shave off a few thousand feet down to a MOCA or even the Minimum Vectoring Altitude (MVA) with your request. The controller is not required to say yes, and they may choose to say no just for the CYA factor of letting you dig your own grave after you smacked terrain you claimed you could avoid. If they say yes, don't expect any safety alerts from the controller. It's up to you to stay safe.
However, if the controller knows you're visual and maintaining your own terrain clearance, you're more likely to get the necessary course twists and turns approved by ATC to keep the valleys a bit closer to your belly.
The Back Door
Can you go even lower? Well, pushing the envelope further hinges on the words, "I can maintain obstruction and terrain clearance in VFR conditions." Usually ATC asks this as a question of the pilot when an MVA is high and the controller wants to let the aircraft descend into a terminal area before crossing the line into a region with lower MVAs. It's also used to approve a climb through the clouds for a VFR aircraft trying to get into the system but below those same MVAs.
We polled controllers for their thoughts on using the same tactic for just cruising along the airway. The consensus, and our own feeling, is that it probably isn't. That said, some freely admitted it is being done with regularity in various places in the U.S.
Since you're PIC, you make the call on what you want to try. We'd probably just cancel IFR or try and get onto some route that lets us cruise lower--perhaps off an airway where we can still be seen on radar but determine our own altitude that just meets the needs of 91.177.
No matter what you do, it's critical to only say you can maintain visual separation when you really can maintain it. While it never hurts to ask for permission to fly a bit lower, the same can't be said for running into a mountain.
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|Title Annotation:||CHART CLINIC|
|Date:||Apr 1, 2007|
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