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File for the big rocks: careful planning, local knowledge, and a few insider tips can make mountain IFR practical and safe in light singles. Here are the basics.

Some will say that mountains and IFR go together like water and oil. While there are situations where small aircraft, IMC, and mountains should not exist in the same place at the same time, an all-out ban isn't necessary.

The key to mountain IFR is suspicious and meticulous planning. The problem most pilots encounter when considering mountain flying is thinking inside the box. A cursory look at en route charts for certain parts of the U.S.--with MEAs often above the service ceiling of general aviation aircraft--might lead one to scrap flights to and through these parts of the country.

Understanding how these lofty charted minimum altitudes are derived offers a way around them and makes flights, that were impossible on initial inspection, possible.

Simple Numbers

In "mountainous areas" under FAR Part 95 (also AIM figure 5-6-2), 2000-foot separation from terrain is required. Off-Route Obstruction Clearance Altitudes (OROCAs)--those big numbers in each quadrant of the en route chart--provide this level of obstacle clearance in reference to the highest obstacle in that geographic area plus four miles beyond. Thus, a mountain even slightly outside the corner of the quadrant creates a high OROCA, even though the terrain adjacent to the mountain may be low and flat.

MEAs not only provide the requisite 2000-foot clearance, but also take into account NAVAID reception. Alpestrine topography necessitates high altitudes for reliable, line-of-sight navigation signals. Both OROCAs and MEAs must be "ignored" to make mountain IFR possible in a light airplane.

The first step when considering a flight through high country is to pull out the local sectional and check out the Maximum Elevation Figures (MEFs). You'll sometimes find that the MEF plus the FAR-mandated 2000 feet will be lower than MEAs in the area.

If the resultant altitude still is too high for your tastes, take a closer look at the sectional to determine the highest obstacle within four miles of each side of your intended course. With RNAV capabilities--probably GPS--you can adjust your course so that no soaring terrain touches a zone on either side of your route.

This method skirts excessive OROCAs and MEAs with regularity. Keep in mind, though, that whenever flying on a random (direct) route, radar coverage is technically required. (Some controllers let this slide, but if you have navigation issues, you could end up you know where without a paddle).

Seek the MVA

Another trick often used in mountainous areas is direct routing while relying on ATC minimum vectoring altitudes (MVAs). According to the FARs, IFR altitudes that are "correct for direction of flight" technically apply only to flight in uncontrolled airspace. Traffic permitting, ATC will allow "incorrect" directional altitudes. But if another airplane comes along, it could spell a deviation or an unwanted climb.

A further advantage of using ATC for altitude help is that radar displays typically isolate high MVAs to areas immediately adjacent to significant terrain features. This translates to the availability of appreciably lower minimum IFR altitudes. Unfortunately, MVAs are not made public, so some help from local pilots and/or personal experience is necessary for relying on this method. It's no surprise that this technique requires radar coverage, which can be sketchy over much of the Rockies below turboprop and jet altitudes. Even in the relatively placid Smoky Mountains out East, radar service can't be assured at lower altitudes. So if you've never tried this idea before, be sure to have a plan B.

Avoid Pesky Turns

Route planning should take the approach into account. This is particularly important considering that airports are often built in valleys. Without proper preparation, you can end up a few miles away from the airport with a mile or more of altitude to lose. Not only does this situation make your life more complicated, it causes unnecessary delay for you (and potentially others) and you risk shock-cooling your engine with a rapid descent.

So how do you avoid this? Examine the weather and approaches that favor the forecast. Plan your route to end at a point at which an approach begins. If possible, plan the inbound routing to allow intermediate step-downs so you're not faced with one big leap down to the initial approach altitude.

RNAV users would be well suited to create "step-down waypoints" where you've determined it is safe and legal to go lower. Prompt ATC for a descent upon passing these homemade waypoints. They may not always agree, but it will at least prompt them to give you lower ASAP.

A valuable tool for these circumstances is the vertical navigation (VNAV) feature of the GPS. Before thinking of mountain flying, learn how to use VNAV. When set properly, VNAV can give you a recommended descent rate to altitude restrictions that you want to meet, reducing mental workload significantly.

An added benefit of planning the route to coordinate with the approach is that it may prevent long, drawn-out procedures. In the hills, it is not uncommon to have to do procedures on your own, mostly due to lack of radar coverage. Don't let the controller bully you towards an IAF that requires a convoluted transition or intermediate segment. Instead, while you're still in radar contact, make sure you're heading to an IAF that provides the simplest form of arrival. While this philosophy does not always work, controllers usually try not to change things around on you unless traffic or other issues arise.

Getting onto the approach is usually easy, though sometimes time-consuming. Completing the approach is where trouble commonly ensues. Mountain IFR naysayers may point to the soaring landing minima that airports at elevation require. Minima of 2000 feet and three miles is not uncommon. Many approaches use visual segments from which there isn't a missed approach--the "land or S.O.L." approach.

Something that mountain fliers do to get around this is to shoot an approach with lower minima at a nearby airport and cruise over to the desired destination VFR following a prominent feature such as a road or river. This transition normally takes place in uncontrolled airspace, allowing plenty of leeway in terms of cloud clearance and visibility. Unmistakably, this is only recommended when very familiar with the area. Newbies who try this are asking for a windshield full of mountain goat.

Working It Backwards

Oddly enough, a similar method can be used when departing. There are some mountain airports without departure procedures (DPs) or take-off minima. Pilots departing from these locations are on their own for obstacle clearance. Since such airports are often many miles from the nearest boundary with controlled airspace, IFR can be conducted without the need for a clearance. Since FAR 91.177 demands minimum IFR altitudes "except when necessary for takeoff or landing," there is a little loophole that experienced mountain fliers take advantage of to get out.

If a planned departure airport has DPs and/or takeoff minima, you can ignore these requirements as long as you are operating under Part 91. You could take on all the responsibility for obstacle clearance, perhaps by using a GPS-assisted climb over the airport or up a valley.

Needless to say, the FAA and NTSB won't have nice things to say if it doesn't work out as planned. Unless you can figure out TERPs clearances in your head, it's a good idea to fly the DP if it exists.

Many DPs are rather onerous and time-consuming. The best advice is to climb like a bandit, not just for terrain but for radar identification. The faster you do this, the sooner you will be able to request direct to something. ATC may let you fly the whole procedure if you don't ask for something else, as they've got enough on their plates as it is.

Something else to keep in mind is that ATC may not be intimately familiar with the DP requirements of your departure point. If the procedure requires you to go to Timbuktu VOR and hold as you climb, you may want to bounce that off of the controller. Local pilots may know of another way out and use it so often that the controller isn't aware of the correct procedure. Ideally, the controller will offer the frequently used substitute. The worst case would be if you start holding unexpectedly and ATC has a fit.

Beyond Procedures

That's not the whole story about flying in the mountains. Density altitude, aircraft performance, icing, turbulence, and hypoxia are all factors you must consider. For example, there will be days when climbs from hot mountain airports will be impossible--don't even try it. You must consider this for both departures and arrivals, because your missed will necessitate a serious climb. Hypoxia has been covered in previous articles ("Punching High," August 2006 IFR and "The 91-Percent Solution," January 2006 IFR).

Although the key words with this kind of flying are "be careful," mountain IFR is certainly doable under the right circumstances. With the proper care, there are all kinds of neat tricks and techniques that can be used to get around the typical, making once "unattainable" flights readily achievable.

In the end, you'll have world of new options available to you for routing and destinations, likely saving you time, money and hassle. And, assuming you're not IMC the whole time, the views aren't bad either.

RELATED ARTICLE: Leveraging GPS for a departure.

Tech-savvy pilots can utilize GPS and VNAV to assist in staying safe when leaving a mountain airport. When the departure calls for a non-standard climb or reaching a certain altitude by a certain point, you can use your VNAV feature in reverse.

Enter the altitude you need by a specific waypoint on the DP and watch the vertical speed required VSR. So long as your climb rate exceeds the VSR--and you comply with any course requirements to stay away from pointy objects--you'll reach the waypoint with sufficient altitude to continue on-course.

When none of the available DPs are in the database, you may notice striking similarities between missed approaches into the airport and the recommended DPs. Use this to your advantage by pulling up an approach whose missed is virtually the same as the DP you need.

By activating the missed portion, you'll have a great boost in situational awareness by having a picture of what you need to be doing.--D.I.

Formerly with the airlines, David Ison is Assistant Professor of Aviation at Rocky Mountain College in Billings, Mont.
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Title Annotation:Instrument Flight Rules
Author:Ison, David
Publication:IFR
Geographic Code:1USA
Date:Sep 1, 2006
Words:1733
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