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Performance in the Real World – Part 2

September 3, 2012/in Tips and technique/by Studentpltnews

Takeoff performance calculations start with a chart from the airplane’s POH but there may be more to the story. We’ll take a look at one of these charts along with the conditions and notes on the chart that many pilots overlook. We’ll also address what to do when the runway just doesn’t fit the mold defined by the chart.

Happy Anniversary

August 13, 2012/in Personal stories/by Studentpltnews

This week I will celebrate the 29th anniversary of my 29th birthday. Birthdays, which are so anticipated when you’re young. I can’t wait until I’m 6 and go to school. I can’t wait until I’m 10 and can take a tractor to the field by myself. I can’t wait until I’m 16 so I can […]

Performance in the Real World – Part 2

September 3, 2012/in Tips and technique/by Studentpltnews

Happy Anniversary

August 13, 2012/in Personal stories/by Studentpltnews

Full Sized Blog Element (Big Preview Pic)

Performance in the Real World – Part 2

September 3, 2012/in Tips and technique/by Studentpltnews

More Than Just the Calculations

In my last post, I discussed Pressure and Density Altitude calculations and their contribution to the total performance equation. In this post, I’ll cover some of the other values in the takeoff equation that we don’t always keep in mind.

When calculating performance for our airplane, we use the charts found in the Pilot’s Operating Handbook (POH) for our aircraft. These charts generally account for density altitude and include conditions and notes to address other factors. When was the last time that you took a close look at the conditions and notes associated with the chart? They are important and are there for a reason.

As an example, the “Short Field Takeoff Distance at 2550 Pounds” table for the Cessna 172S lists the following conditions:

Flaps 10°
Full Throttle Prior to Brake Release
Paved, level, dry runway
Zero Wind
Lift Off: 51 KIAS
Speed at 50 Ft: 56 KIAS

It also includes the following notes:

Short field technique as specified in Section 4.
Prior to takeoff from fields above 3000 feet elevation, the mixture should be leaned to give maximum RPM in a full throttle, static runup.
Decrease distances 10% for each 9 knots headwind. For operation with tail winds up to 10 knots, increase distances by 10% for each 2 knots.
For operation on dry, grass runway, increase distances by 15% of the “ground roll” figure.

Many of these items are related to technique and aircraft configuration and are easy to comply with. Some can be tougher.

Take the “Paved, level, dry runway” condition. This seems simple enough but have you checked the grade on the runway at your home airport? What about the runway where you are planning to land and will have to later takeoff? Do you know where to find this information? Do you know how it will affect your takeoff distances when you find this information?

Runway slope information is published by the FAA in the Airport/Facility Directory. The information can also be found on the Airport Diagram or Airport Sketch for the airport in the Terminal Procedures Publication (approach plates). Many commercial sources, GPS databases, and pilot apps also include the information.

Looking at the Clermont County / Sporty’s Airport, we find a slope of 0.9% uphill on runway 22 and the same slope downhill on runway 4. This equates to about 32′ of elevation change from one end to the other of the 3566′ runway. The grade is not a consistent slope of 0.9% but there isn’t information readily available that tells us what the slope is at different points along the runway so we’ll stick with the 0.9%.

The chart in the POH doesn’t provide any indication as to what we should do when the runway is not “level.”

For help in addressing this adjustment, I would look to an expert in flying on “non-level” runways. The late Sparky Imeson, author of the Mountain Flying Bible Revised suggests the following rule of thumb with regard to gradient. For a 1% upslope, which is approximately runway 22’s slope, increase the takeoff distance by 7.5%. While not specified on the Imeson family’s website, this should be 7.5% of the ground roll. If a 2% upslope, use a 14% increase; 4% upslope, 25.5% increase; and 6% upslope, 39.5% increase.

Another aspect of the notes which has no resolution in the POH is departing from a wet or otherwise contaminated runway.

A wet runway will change the friction between the tires and the surface. While this may decrease friction, I wouldn’t expect it to shorten the takeoff roll.

Standing water will increase the takeoff roll. This is due to “displacement and impingement drag” as the spray from the tires is displaced and strikes the aircraft. The FAA’s AC 91-6A regarding Water, Snow, and Slush on the Runway hasn’t been updated in over 30 years. At that time there was no clear engineering data on how much water or slush on the runway affected the takeoff roll.

You should not attempt a takeoff when standing water or slush on the runway is more than one half an inch deep.

Imeson’s website has some rules of thumb regarding surface contamination as well.

Cessna recommends increasing the ground roll figure by 15% when taking off from a dry, grass runway. This guidance may be incomplete as it does not account for the length of the grass or the roughness or softness of the surface. 15% will be fine when the grass is short and the ground is firm and smooth but may be insufficient if the grass is longer or the ground is softer or rougher. Using a soft-field technique rather than the chart’s indicated short-field technique (see Note 1 above) may also influence this distance.

All this said, the chart in the POH is our best place to start on any takeoff calculations. You just have to keep the conditions and notes in mind and know when they won’t account for your current situation. Have fun and stay safe!

Happy Anniversary

August 13, 2012/in Personal stories/by Studentpltnews

This week I will celebrate the 29^th anniversary of my 29th birthday. Birthdays, which are so anticipated when you’re young.

I can’t wait until I’m 6 and go to school. I can’t wait until I’m 10 and can take a tractor to the field by myself. I can’t wait until I’m 16 so I can drive. There are reasons you want to be 21.

The birthdays just become numbers after you get to be middle aged. I am starting to qualify for some senior discounts so that is a plus, but now birthdays become a time to look back and reflect on a blessed life. I had strict but loving parents. I am married to the most beautiful girl (both outside and inside) in the world and I go to work at an airport. So I have decided to use this space to look back at the 6 decades through which I have lived and reveal what I believe to be the major advancement in general aviation for each one.

1950’s – The Nose Wheel. The decade of my birth saw wide fleet-wide adoption of aircraft with the third wheel under the nose instead of the tail. The first 5 decades of aviation was dominated by so called “conventional gear” or tail-wheel aircraft. Visit the “legacy” aircraft flight line at any big air show and you will see rows of Cubs, C-195s, Stearmans, Staggerwings, and Electras. Early airports (like Bowman Field (KLOU) in Louisville, the oldest continually operating airport) were little more than big flat spots where general aviation airplanes could always land into the wind. Their nose high attitude on the ground kept the propeller safely clear of the uneven turf.

With the advent of heavier aircraft the turf was replaced with pavement. By moving the mains aft and propping up the nose of the airplane manufacturers discovered on ground visibility improved and there was a marked reduction in ground loops during those perilous moments between touchdown and chocks. I guess this trend toward metal nose wheel airplanes started in the 1940s with the Bonanza, but I contend it was the 50’s when the Pacer became the Tri-Pacer and the 170 became the 172 marking the domination of nose wheels we still see today.

1960’s – “That’s one small step for man, one giant leap for mankind.” What did President Kennedy’s declaration vowing to “Before this decade is through, we will put a man on the Moon and return him safely to Earth” have to do with general aviation? Well, for one thing, it inspired a generation of pilots (including this one) to get excited about all things aeronautical. But more importantly technology needed to get smaller and lighter if they were going to reach escape velocity. Tubes were replaced by transistors which were replaced by silicon chips. Power requirements were reduced and computing power increased. All these innovations were forerunners leading to modern avionics, smart phones and iPads upon which we rely today. A guy named Hal Shevers started selling portable aviation radios out of the trunk of his Studebaker, a business that gave birth to Sporty’s Pilot Shop.

1970’s – Expansion of the aviation infrastructure. During this decade, the number and quality of airports dramatically increased. Rural communities came to understand that economic development would come on an airplane, not a Greyhound bus. Corn fields became airports. Piper, Cessna and Beechcraft were producing tens of thousands of airplanes a year. As a testament to industrial efficiency, those airplanes were all made of aluminum and had engines built by Lycoming or Continental with mechanically tuned radios mostly from King or Narco. Almost every FBO was a dealer for one of the manufacturers and thousands of us were learning to fly. It is the decade in which I first flew an airplane opening the door to many adventures.

1980s – The birth of the internet. While not fully developed as the World Wide Web, computers were being linked and email became possible. Prior to this technology, teletypes and fax machines were the way electronic documents moved. Indeed the numerous Flight Service Stations (FSS) relied on these technologies for the surface observations, forecasts and radar maps they provided to pilots of the era. To get a weather briefing, a pilot would either call or visit in person one of the several dozen FSS facilities. Many had local radar, but for cross country planning, the information we received may well have been over an hour old.

Nowadays, we take out our phone, open an app and receive near real time information on weather and NOTAMS from across the country – courtesy of the internet.

1990s – You are here. Sure, transoceanic airliners and high end corporate jets had inertial guidance and LORAN systems for navigation, but for most of us, navigation and situational awareness was divined by some combination of pilotage, dead reckoning and aligning needles from VORs and ADFs. A competent pilot knew where they were in general, but often, his last known position was the approach end of their departure runway. In 1989 the Global Positioning Satellite (GPS) constellation became operational. The 1990s saw first the introduction of hand held GPS devices into the general aviation cockpits. These incredible little boxes were both accurate and affordable providing both a course line and accurate positioning along it. We marveled at being able to know where we were – exactly. So accurate and reliable pilots would remark, “If it says you are here and you don’t think so, you are wrong!” In 1998 Garmin introduced its GNS-430 Com Navigator relegating the need to align needles to determine a fix to the dust bin of Instrument Flight Rules history.

2000s – The information age hits the cockpit. Avidyne introduces its “glass” displays in the cockpit of Cirrus aircraft. Garmin soon follows with the G1000 in Cessna and Diamond airplanes. Soon the 10 – 17 inch “monitors” are in every new aircraft save some special utility and sport aircraft such as Huskies, Maules and Citabrias. Pilots could literally fly coast to coast and never take a chart out of their flight cases. All the terrain, airways, and airports are graphically presented on Multi-Function Displays (MFDs). Airport information, right down to the phone numbers of the nearest hotels were all stored in the avionics. Early in the decade, Bendix King launched its ground based Flight Information System (FIS) providing near real time weather in the cockpit. Traffic Avoidance Systems (TAS) from King, Ryan and Goodrich became more affordable and prevalent. XM Satellite Radio teamed with WXWorks to stream satellite based weather into the cockpit (along with a couple hundred audio stations). Not having the line of sight limitations of the ground based system those FIS stations were eventually abandoned. This technological revolution so greatly increased situational awareness we all assumed those Controlled Flight Into Terrain (CFIT) and continued VFR into IMC accidents would be eliminated. Unfortunately, it seems pilots are destined to fly into rocks and weather for which they are unprepared.

20 teens – So far it’s the iPad. Only two years old, this decade has seen the nearly ubiquitous acceptance of tablet computers (and their accessories) by pilots. Everything from flight planning, performance planning, weight and balance, cross country navigation, to logging the flight can all be performed on these 10 inch wonders. GPS/ADS-B receivers like the Stratus provide in-cockpit weather and situational awareness for Champs, Gulfstreams and everything in between.

Powered flight is 109 years old. I have been around to see more than half of that. After reflecting on the past, I like to ponder the future and wonder what the next six decades will bring. I offer the following predictions.

The rest of the teens – New engines, new fuels. I predict leaded gasoline will be banned in California. This will lead to the development of new fuels and engines to use them. Cessna introduced its Compression Engine, Jet A burning Skylane at AirVenture this year. Pipistrel has an airframe that will tolerate alcohol in its gasoline. Propellers will become more efficient with new designs and materials allowing us to squeeze more knots from each gallon of whatever we are burning.

2020s – Next Gen goes fully operational. ADS-B in/out technology will allow us to not only know precisely where we are, but where all the other airplanes are around us. ATC can make better use of available runways and offer altitude and speed advisories that will eliminate the need to ever hold at a fix. Unmanned Aerial Systems (UAS) will share the skies with those of us who still desire to fly. Airliners are certified single pilot eliminating the predicted pilot shortage.

2030s – Advances in materials allow airplanes to “morph”. As airplanes have gotten bigger and faster, so has the runway required for them to safely take off and land. My prediction here is that airplanes will not only be able to configure gear and flaps, but the wings and control surfaces themselves, small and thin for high speed cruise – large and thick for slow take offs and landings allowing the largest airliner to operate out of runways less than a mile long.

2040s – Autonomous piloting of both airlines and private airplanes. Aircraft manufacturers are able to eliminate the part that fails the most often. The pilot.

2050s – Teleportation. Just look at an old Star Trek episode.

Happy anniversary.

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Performance in the Real World – Part 2

Happy Anniversary

Performance in the Real World – Part 2

Happy Anniversary

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Performance in the Real World – Part 2

Happy Anniversary

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