“Diving and Driving” on instrument approaches is dead. So are some of the pilots who used to use this frequently taught method for flying non-precision instrument approaches. If you didn’t get the memo, you’re not alone; some CFIs are still teaching this outdated practice even though the FAA announced—in 2001—that our industry should discontinue “dive and drive.”
Quoting from my Max Trescott’s GPS and WAAS Instrument Flying Handbook, non-precision approaches
“resemble a series of steps, like those found in a staircase, and nothing prevents you—other than your good judgment—from descending as rapidly as possible at each step. “Diving” at each step was originally thought to be advantageous on the final approach segment, since it allowed more time to “drive” level at the MDA while looking for the airport.”
Hurrying to get to the MDA to “look for the airport” had some merit before GPS-based instrument approaches became prevalent. One corporate pilot told me he felt lucky to come within half a mile of an airport when flying NDB approaches with an ADF receiver. But the airport could be on either side and pilots had to look left and right to search for it while flying at minimums. VOR approaches are more accurate, but still leave much to be desired.
In a GPS world, there’s far less uncertainty when flying non-precision instrument approaches. There’s no ambiguity about when you reach the missed approach point and typically the airport is directly in front of you. True, not everyone that flies IFR has an IFR-certified GPS in his or her aircraft, but the world is moving that way. For example, Garmin sold more than 100,000 of the now discontinued GNS 430 and 530 GPS receivers.
The problem with dive and drive is that “diving” at a high descent rate may cause a pilot to inadvertently lose control, or fail to level off at the proper altitude. In fact, the Flight Safety Foundation’s study Airport Safety: A Study of Accidents and Available Approach-and-Landing Aids found that the accident risk for flying non-precision approaches is five times higher than for flying precision approaches.
Quoting again from my book,
“In 2001, the FAA announced that the industry should discontinue the use of a ‘dive and drive’ process on non-precision approach procedures, since they contribute to controlled flight into terrain (CFIT) accidents, the leading cause of fatal commercial air accidents worldwide. Instead, the FAA advocates the use of procedures and training for a stabilized continuous descent on non-precision approaches. Some airlines have gone so far as to implement procedures that require pilots to immediately initiate a missed approach if they don’t see the airport when they reach the MDA; they are not permitted to continue ‘driving’ to the MAP.”
For pilots using an IFR-certified, WAAS-capable GPS, LNAV+V, which displays an “advisory glide slope” on some non-precision approaches, is a good substitute for the “dive and drive” process. Another best practice for flying a stabilized descent is to estimate the descent rate required for each segment of an approach, by comparing the altitude loss required to the number of miles available to descend for each segment of the approach. Knowing your ground speed, it’s relatively easy to estimate the rate, in feet per minute, at which you’ll need to descend during each segment.
So spread the word: Dive and drive is dead. And if someone argues the point, tell him he must have missed the memo!
The opinions expressed by the bloggers do not reflect AOPA’s position on any topic.