Unicom

October 2003 Issue




Unicom 10/03: Never Say Never

I never conduct overweight ops, except when I do. Some rules of thumb to live by ... or not

Your July article “Fat and Happy” touches a subject aviation writers don’t dare discuss publicly but is a fact of flying life. I have been flying for 27 years, logging 2,000-plus hours. I own a Cessna Turbo 206 and a Ram Series VII Cessna 414A.

I have always followed the POH when it comes to loading an airplane and very seldom overload. On those occasions when I have done it, I follow this personal strict criteria:

1) Never go beyond 1 percent, a maximum of 2 percent, which in the case of the 414 is around 70 to 140 pounds, which will be burned in the first 30 minutes.

2) Never exceed aft cg limits.

3) Never exceed zero fuel weight.

4) Never even consider the possibility of using that 1 percent to 2 percent unless the runway is 50 percent longer than the balanced field length for maximum gross, including density altitude considerations.

I have a question you might help me to solve: The Ram Series VII conversion specs call for 315 fpm best single engine rate of climb, as opposed to 270 fpm for a stock 414A. Since all these figures are for new equipment, I have to realize some reduction in performance for half-time engines and props.

Is there a way or rule of thumb to approximately calculate the reduction in single engine rate of climb when you exceed the max gross?

-Jose Iturbide
Via e-mail


The rule of thumb is to not exceed max gross weight in the first place. If you really want to be a test pilot, you might try comparing the excess horsepower available in the stock single-engine configuration with the excess single-engine horsepower of your RAM conversion. You might be able to come up with a comparison of power-to-weight ratios in each configuration that would allow you to estimate single engine rate of climb. However, recognize that you’re on your own in assessing whether the calculations hold up in real life.

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G Loading Vs. Aerodynamic Loads
Your article “Stress Encounter” [Accident Probe, August] reminded me of an early 70s Navy F-8 Crusader accident where two aircraft were exiting the SOCAL training area at 500+ knots when one aircraft hit wave turbulence coming off the foothills west of San Diego - the wingman watched as both wings folded up and snapped off.

Your statement that “Va goes down linearly with decrease in weight because the airplane becomes more subject to aerodynamic loads as it gets lighter” may be misleading.

While it is true that, as aircraft weight decreases the ability of the wing to generate g-loading increases, the wing still generates the same maximum aerodynamic force at its maximum coefficient of lift, irrespective of aircraft weight. A wing at 3.0 G’s at CLmax at 132 KIAS and aircraft weight 3600 lbs would be producing 10,800 pounds of lift, plus enough extra lift to counteract the downforce of the horizontal stabilizer.

So, if CLmax produces 10,800 pounds of lift on this aircraft at 132 KIAS, by reducing weight to, say, 3,000 lbs, your G meter would now be reading 3.6 G’s, but the aerodynamic load is the same. The pilot, however, will be experiencing 3.6 G’s on his anatomy.

It might be postulated that the airplane’s speed in this case was more than 132 KIAS, and still the cause of wing failure to gust loading, Also allow that since dynamic pressure increases as the square of velocity, a 10 percent increase in velocity leads to the wing being able to generate 21 percent more lift.

I regret that the above does little extra to solve the cause of the mishap, which, bottom line, was probably the pilot’s inability to avoid really bad weather, but it was a chance for me to try to sell my aerodynamic analysis of the situation.

-Bruce Sheppard
Via e-mail


Gee thanks. Your analysis works, and illustrates why you should slow down when turbulence is expected.

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Traffic Advisories on the CTAF
Ron Levy is right [Instrument Flight, June], asking for advisories should be superfluous. But some airports are frequented by pilots who assiduously announce their position and intentions and some are frequented by pilots who just as assiduously don’t announce.

I once landed at a Northern California airport and confronted a 172 coming the other way on the runway – a student pilot at the yoke with instructor next to him. When I was through venting, the instructor allowed as how he had turned off the radio so he could instruct better! (Legal? Yes. Stupid? Absolutely!) At the same airport I met a crop duster coming from the other end of the runway, practicing touch and goes with no radio. All the requests in the world wouldn’t have gotten a response from either of those morons but to assume it is unnecessary is like saying there’s no need to see and avoid because you’re on flight following and ATC is watching over you. Moral: ask for traffic advisories and announce your position and intentions.

-Lauren Ward
Via e-mail


You characterize the two offending pilots as “morons,” yet they’ve done nothing that’s illegal or inherently dangerous, in our opinion. Remember that NORDO happens, although we dislike the instructor’s attitude of turning off the radio. Perhaps if the windsock or A/FD clearly favored the runway you’d selected, we’d come down more strongly on your side.

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More on Idiotic Phrases
I thought on Levy’s article “IFR Without ATC” [Instrument Flight, June] was an excellent article. What was an eye opener were some of the responses to this article in Unicom of the next edition, particularly in regard to “idiotic phrases.”

I agree with Ron Levy that the phrase “any other traffic in the pattern please advise” is not recommended by the AIM and not appropriate. I believe that flying up to an airport traffic pattern and then asking and expecting everyone else to report in to you is incredibly selfish and discourteous to fellow pilots, especially in busy regions.

It taxes everyone else to compensate for your complete lack of preparedness to enter the airport environment. It amounts to a public declaration of ignorance. Starting 10 miles out, everyone should be tuned, listening and scanning for no-radio traffic.

While I will not speak of remote airports regarding weather reporting, for most airports there is a myriad of weather sources – including ASOS, AWOS, HIWAS, nearby ATIS frequencies, FSS and Flight Watch – to prepare a pilot well before reaching the airport environment. Anyone in this kind of airspace who doesn’t know the winds and altimeter long before reaching the airport environment is out of touch with the planet.

Also, any assertion that we should use poor procedures to compensate for other poor procedures in the hope that the combination of poor procedures will equate to an overall good procedure certainly raises an eyebrow.

The article and the editors responding comments in the follow on edition quite appropriately emphasize the importance of standardized procedures. If it is in the AIM, we should do it. If it’s not, we shouldn’t. If you don’t agree, make your case to change the AIM.

-Anthony Esteves
Hillsborough, N.J.


We agree with most of your reasoning. There are some things in the AIM we think are boneheaded and should be changed. This, however, isn’t one of them.

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Is Quicker Better?
I certainly don’t read much about noise management in the aviation magazines, but you take it up in “Shut the Prop Up” [Enforcement, August] and that is a good thing.

By keeping noise down we can hope for restrictions to remain unchanged. By not bothering we are most likely helping the process of restricting airport operations around built-up areas. However, I would like to try to clarify a few minor matters in the article. The article claims “you may gain altitude more quickly climbing into a stiff headwind,” which reminds me of the pilot who liked to open the cowl flaps a bit when he cruised in tailwinds. “Climbing at Vx will get you higher quicker,” as stated later on, is in the same league. No, it will not. Compared to climbing at Vy it will get you higher slower.

By definition, Vy is the airspeed that will make the aircraft gain altitude most quickly, and wind isn’t a factor.

“A short-field take-off will give you greater altitude sooner.” Well, maybe. For the part of a short-field take-off that implies flaps deployment, no. Flaps make (almost) any airplane climb more slowly, and more importantly, slow the airplane down so that it will remain above noise sensitive areas for a longer time. But for the part of short-field take-off that calls for using the runway from the very beginning, that is bound to reduce noise compared to any intersection take-off.

-Henrik Vaeroe,
Roskilde, Denmark


With respect to the notion of getting higher quicker, Mr. Geier’s intent was to describe a climb that gets the airplane higher before it gets to the microphones or other sound-sensitive area on the ground, rather than as a function of time. Headwinds, Vx and partial flaps do just that.

The important considerations are whether the goal is to get as high as possible before crossing the airport boundary, to minimize time over the surrounding community, or to cross over a fixed point (such as microphones) with as small a sound footprint as possible. Your operating technique should take that goal into account.

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Noise Reduction and Safety
Your article “Shut the Prop Up” [Enforcement, August] places the importance of safety lower than regulations made by irresponsible local politicians. Breeze Geier’s advice to “reduce RPM during the climb if, of course , it does not compromise safety” will be interpreted as a courtesy RPM reduction as soon as the plane is clean, in a stable climb, and above local obstacles. The problem is in the assumption that pilots have the gift of clairvoyance.

Unfortunately my recent check pilots drilled this bad practice into my head. Older instructors had more sense when they preached that altitude is your friend, first fly the airplane, and don’t touch any power (except to follow the POH limitations) until you are established en route.

The crankshaft of my Beech V35B Bonanza broke when I brought the RPM back outbound at pattern altitude. This obviously creates a problem in a single-engine airplane, which the lawmakers disregard as they pander to those homeowners who gladly came to the airport area to get lower priced land.

Safety advocates must consider more than just the airplane since it would hurt if an airplane fell on your head.

Pulling back the RPM did not break the crank, but changing the torque stress did trigger the time of failure. Most IO-520 failures are in twins where the noise is greater and the risk of triggering an engine failure with power changes is usually more tolerable and unreported.

Note that most abrupt power failures not related to fuel starvation are associated with changes in power settings. Years ago in a Tripacer my power went to almost nothing as I leveled off. The thermal change broke spot welds inside the muffler and the guts shifted so as to obstruct the exhaust.

This problem was common enough that a corrective AD came out in about a year. Others have triggered piston breakage with power changes, which must wake you up.

For single engine operations, you recommend adding an unnecessary aviation safety risk at a very poor time of flight. I hope that none of your readers is hurt by this bad advice.

-Sherman Francisco
Rockville, Md.


Despite years of trying, we have found no evidence to support the occasionally repeated claim that “most abrupt power failures not related to fuel starvation are associated with changes in power settings.” This, in our book, falls into the category of an old wives’ tale, your conviction made stronger by anecdotal experience.

Lowering RPM by 100 reduces power output by about 3 percent – roughly the same as a 20-degree rise in temperature. Fly through some rain and you’ll easily get that kind of power change – and when you’re controlling the prop you can make the reduction smooth.

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Clarification
I read with interest the response to “Silence. Twice, in Fact” [Learning Experiences, June] the advice offered to the Mooney pilot with suspected induction icing, including the statement “The problem could have been cured by pulling alternate air.”

The article does not divulge which Mooney was involved; however, since the pilot mentions “ram air” and “four little holes” we assume it was a Mooney 201 (M20J).

There is no alternate air to “pull” in the Mooney M20J. Alternate air in the Mooney is via a spring-loaded device, over which the pilot has no control (and which has been the subject of SBs and AD 95-26-16R1 in the past).

-Rae Willis
Via e-mail


Given that we used to own a Mooney M20J with the ram air removed, that was one piece of advice we should have known was bogus. And you are correct in that the spring-loaded door has been the subject of an AD to ensure that it operates properly.