Your article “Keeping Me In Suspense,” September 2014, nicely explains the purpose of the OBS button on the Garmin GNS430/530 series when performing a missed approach. The GPS unit will “suspend” and stop displaying navigational guidance until the OBS button is pushed upon reaching minimum altitude. Although unrelated to an approach, this is the perfect time to mention the second purpose of the OBS button on the Garmin GNS 430/530.

By pushing the OBS button while on a flight plan, the next waypoint becomes a VOR with 360 radials. You can rotate your OBS dial to the radial you select and intercept it. This comes in very handy, for example, when trying to intercept an airway or the extension of a runway.
David Shepherd
Via email

Good point, and one we should have put into the article.

Climb flap
Mike Hart’s article, “Max-Gross Weight Ops,” in September’s issue has a conceptual/technical error that could mislead readers. He describes paralleling or circling near a ridge line, climbing with a heavy load in his Cessna 180. In the article, he explains that he “nursed the flaps out.” Goodness, no.

When the runway is limiting, the aircraft needs more flaps, but climb will suffer. If climb for an obstacle is a limiting factor for the takeoff, the aircraft needs less flap extension, but takeoff roll will be longer.

Granted, Mike may have noticed a brief burst of climb when he nursed out his flaps, but the physics rapidly takes over. His drag increases, climb angle and rate both eventually decrease. By the way, same goes for gliding: Keep those flaps up to maximize climb (not takeoff) and glide performance.
I hope your readers understand this. It’s important.
Martin Giesbrecht
Via email

What Mike (and we) meant to say is that he gradually retracted his flaps after taking off, instead of retracting them all at once. You’re right: extending them for a better climb is a no-no.

Two More Things
Great article, but a couple of items Mike Hart fails to mention are flight control inputs and proper leaning as they effect a max gross weight, high-density altitude takeoff.

Above sea level, proper leaning of a normally aspirated engine is imperative, as are proper and appropriate flight control inputs. Also, one must anticipate that a max gross weight takeoff roll will be much longer than expected, so do not force the airplane into the air prematurely. Instead, allow it to fly off, even if you use all the runway. If there are trees or other obstacles in your way, you obviously haven’t done your homework. Almost 100 percent of the time, forcing the airplane into the air prematurely will not improve the situation, and sometimes worsen it.

Second—and I can’t emphasize this enough—finesse the controls. Nothing will degrade performance more than overcontrolling the airplane when performance is marginal. You must extract the needed performance from the aircraft, but you must do it gently, otherwise it bites back!
Jim Piper
Via email

More good points. We certainly always try to handle the airplane gently, regardless of how it’s loaded. But heavy (and often with a CG near the aft limit) is definitely a good time to practice finesse.

Installing AOA
I would like to add to the comments on angle of attack indicators. I think they are a great addition, but I wonder if we are using them correctly. I recently purchased an old Navy trainer, and decided to install one of the systems described in your article.

The calibration instructions state, rather emphatically, to set the on-speed doughnut AoA at 1.3 VS, i.e., clean. That sent me back to Aerodynamics for Naval Aviators to see if there is a relationship between clean stall speed and optimum approach at landing flaps. None that I could find. The manufacturer seems to think doughnut AoA is for the downwind leg, but that’s not where people stall.

I have set mine at weight-adjusted, crossing-the-fence airspeed, with a 500-fpm rate of descent, close to what we used for carrier landings in my other life. Others may have a different preference, but shouldn’t this system be configured with landing flaps?
Dave Oberholtzer
San Diego, Calif.

What does the manufacturer say?

No Time Like The Present
After reading Amy Laboda’s September article, “Practical Preflights,” I thought I’d make a radical suggestion: Replace the preflight with a post-flight inspection.

A thorough post-flight will find anything that a preflight will, and has the advantage of allowing you time to repair/have repaired any discrepancies you find. To me, this is far preferable to arriving at the ’drome to go aviating and find a non-airworthy airplane.

If you have done a good post-flight inspection, all you have to do is see if there is air in the tires and check for puddles under the machine before launching. I have done it this way for more years than I care to think about, on aircraft as varied as a Beechcraft G-17 Staggerwing, Ryan ST-A and even a P-51 Mustang. It’s also worked well with modern aircraft, up to a Beechcraft Duke.

A couple of stipulations: The airplane must live alone in a private, bird-proof hangar, (we don’t have mud-daubers in Southern California), and I am the only pilot flying the airplane, or at least the next pilot flying it.
Jeff Cannon
Via email

Performing some kind of post-flight inspection is always a good idea, no matter who will fly the aircraft next. Pilots who have the “luxuries” of owning their own aircraft and flying it exclusively can reasonably expect to find it pretty close to the same condition they left it. But fluid levels—engine oil, brake fluid, hydraulics and fuel—still need to be checked before flight, if only for confirmation.

Presuming no critters have access and it’s a relatively dry environment, performing a post-flight walkaround and resolving any discrepancies well in advance of the next flight may be all that’s needed. We check all these boxes, too, but still take a close look, just in case.


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