Magnetic Field Fuel Level Senders - Resistance Output

 Another Day And Another New Fuel Level Sender Configuration @ CiES 

While we discussed the Universal Output Sender in a previous blog post, it's much better to talk about an actual fuel level sender we are sending off to it's intended OEM manufacturer.   

This new configuration will output an equivalent resistance to be read by a gauge or the aircraft MFD.   While it appears on the surface to be easy it is actually the result of a 3 year effort to provide an output suitable for the aviation environment.   

Our senders are natively frequency output based, and this output has proven to work very well in our OEM and retrofit applications for Cirrus Aircraft,  but what we needed to do was convert that frequency to either a voltage or resistance output.

So we manipulate this native output to provide a variable voltage or a variable resistance.  

This unit for a new customer contains everything we wanted to provide;

• Frequency Output Fuel Level
• Slave Sender Input
• Resistance Output Fuel Level
• Fuel Temperature 

It is the culmination of making a Fuel Sensor that is compatible with most platforms out on aircraft & helicopter platforms in the field.

Cessna Cardinal 177 Fuel Sender Design Process

Can we offer a Retrofit CiES Fuel Sender for your aircraft. 

What are the steps we need to take: 

New Cessna 177 Cardinal Fuel Level Sensors 

• Obtain a a set of old fuel level sensors from the aircraft we are considering.  If the part numbers for the senders match the aircraft they are on, we are good to go.

• Ideally this aircraft should have a strong user base with an owner base that demonstrates their willingness to embrace new technology with their pocketbook.

• Discuss the compatibility with commonly installed MFD components or instruments.  CiES  Fuel Level Senders now has the capability of driving even old analog gauges in the aircraft (Universal Fuel Level)..

• Our market is the pilot / customer that is more concerned with fuel level issues and wants the required fuel level instrument in the panel to have the  capability of multiple point calibration.

Old Cessna 177 Stewart Warner and Leigh Fuel Sensors 

• Evaluate the existing sensor design -  For example the bends in these sensor arms are either to assist in installation and removal of the fuel sensor or to clear aircraft structure in the fuel tank.

• As our sensor design allows for an easily detachable arm - these bends might not be necessary and simplify the design greatly.

• We then proceed to manufacture a prototype sensor with our best guess for geometry.

Cessna 177 Cardinal Fuel Tank - Internal Shot

• Check the sensor in the aircraft fuel tank.  As you can see in the illustration - in this case the simple arm design works better in the tank and sweeps a better fuel volume being closes to the Spar and maximum chord point.

• At this point we qualify the design with drawings and procedures for the completed unit so that we can send these files to the FAA to have this configuration added to our TSO.

Fuel Tank with Prototype Sensor Installed 

• Once we have approved drawings we can can produce the required sender with a TSO Tag attached.

• The fuel tank is then drained, the aircraft leveled and braced only then is the zero fuel amount added.  There should be movement of the sender to be able to record an accurate zero fuel level, this is an absolute requirement.

• Fuel is then added to the tank incrementally and accurately to obtain data points for calibration.  We direct the installer to take special caution to insure tabs fuel value is accurately recorded by the fuel display.

• Equally the installer needs to insure full fuel level per the POH is also accurately displayed.   

Note:  All aircraft fuel tanks are built with expansion volume - Full fuel per the POH may or may not be to the neck on the filler plate.  This is very important as the aircraft will probably be fueled in the future on a ramp -

Varying fuel tank angles caused by imbalanced fuel filling - filling one side before the other

or 

The angle of the ramp typically created to drain water from the ramp surface.

Both of the above have an effect on apparent aircraft fuel level from simple visual observation.  

• A confirmation of entered fuel level and actual fuel level when the aircraft is in stable cruise flight may allow the pilot to correct for an erroneous starting fuel level value. 

• The final result is a happy customer with a new fuel sender design that has hundreds of data points to describe the fuel tank contents on their new MFD display or instrument.

Note:  While this seems to be an involved procedure - accurate fuel display on an aircraft requires this level of detail otherwise you might not get the information you need.

PA28 Piper Cherokee - Lands in a Field -

MAY 6, 2014

CHAMBERSBURG, Pa. — The pilot of a Piper PA-28 Cherokee with engine failure successfully managed an emergency landing at about 5 p.m. Tuesday on a Greene Township, Pa., field.

Northern Maine resident Brady Henderson, 35, walked away from the incident. He said he was a bit sore.

Henderson said he noticed the single-engine plane, which he has owned for six weeks, was having problems about six minutes before putting it down in a field across the road from Franklin County Regional Airport in Chambersburg.

The Federal Aviation Administration was on the scene investigating the incident.

Henderson said he was in communication with air-traffic controllers in Harrisburg, Pa., and attempting to land on the Chambersburg airport’s tarmac. Unable to set up the approach appropriately, Henderson opted for the field as an alternative.

Henderson, who has been flying for several years, is licensed for visual flying and has practiced grass field landings previously. While visiting family in the area, he decided to do a practice flight Tuesday afternoon.

The plane remained intact after the rough landing. Crews with a pickup truck hauled it to the airport.

Henderson said he was unsure why the engine failed and would hire a mechanic to evaluate the aircraft.

Jennifer Fitch/Staff Writer HM MEDIA 

PA28 Piper Archer - Out of Fuel - Land on Road in Hungary

Nov 14 2010  - Piper PA28 Archer III Lands on a Road 

A very lucky day tonight for a pilot of a D-registered Piper Archer who safely performed an emergency landing on a highway on the outskirts of Brno around 18.00 local time (after dark).

The aircraft was en route from Germany to Hungary when its French pilot reported shortage of fuel to the air traffic control and notified them of his intent to land on a highway. The crew sustained no injuries, but the aircraft badly damaged one of its wings by hitting a street lighting poles.

PA28 Hits the Road - Out of Fuel

Out of Fuel, Pilot Lands on Highway

Flying Magazine

By Stephen Pope / Published: Jul 16, 2013

Related Tags: Pilots, Adventures & More, News

Courtesy of WSOC

Enlarge Photo

A North Carolina pilot late last night successfully landed his single-engine Piper Cherokee between cars on Highway 321 a few miles short of Hickory Regional Airport after running out of fuel.

The pilot, Eric Klein, told a reporter for WSOC that when he ran out of fuel he was too low to make the airport and so he decided to set his airplane down on the northbound lanes of the highway, using the lights from the cars as a guide.

“I was coming back from Clarksburg, West Virginia, and should have had three hours of fuel left in the plane,” Klein told the news station. “I had excessive fuel burn for some reason and only had two hours and 10 minutes, and ran out of fuel about five miles short of the Hickory Airport.”

Klein managed to land his airplane without hitting anything, bringing it safely to a stop on the road in Granite Falls, North Carolina, at about 11 p.m.

No NTSB Action 

159 Piper PA28's - Have Suffered Fuel Exhaustion in the last 20 yrs.

COVINGTON, TN -

(WMC) – The small plane that went missing around 11 a.m. on Wednesday was found crashed in a wooded area two hours later.

"I really don't understand how he could survive something like that. People are resilient. It just wasn't his time," said pilot Ben Baker, who helped in the search

According to the Tipton County sheriff, the pilot's name is Kent Wingate, 62. Firefighters on the scene say Wingate was unconscious, but his heart rate and blood pressure were stable. He was taken to Regional Medical Center in critical condition.

Wingate and his Piper Archer single engine plane were found near the Hatchie River in Lauderdale County.

The plane went missing as it prepared to land at Covington Municipal Airport. The airport's manager said that Wingate told him he was out of fuel and was going to land the plane; it never landed.
Images from Chopper 5 show the plane wedged in thick trees about two miles north of the airport. The crash site was located by tracking the emergency signal being transmitted from the plane.

"It was so thick back there in the area of the backwater ... Some of the slews, the foliage really thick," said Tipton County Sheriff Pancho Chumley.
A boater on the Hatchie River was flagged down by emergency personnel to take them across the river to the wreckage.


Wingate was flying into town for a funeral. He retired from the United States Air Force where he was an aeronautical engineer.

.According to our NBC affiliate, WDTN, Wingate lives in Xenia, Ohio, which is a suburb of Dayton. He works at Sinclair Community College.

"Kent Wingate is the chair of the Aviation Technology department," Sinclair spokesman Adam Murka said in a written statement. "

Copyright 2014 WMC Action News 5. All rights reserved.  

When Kent left Dayton Wright Brothers airport on Wednesday morning he had calculated his fuel to include the average 20 knot headwind to Covington, TN. 

He stated he would have 13 gallons left in his tanks when he landed which would provide approx. 1.5 hours of available fuel remaining. He topped of the airplane before departure. He flew 3.9 hours at an average fuel burn of 8.5 gallons an hour.

As anyone who’s flown the older Piper aircraft know, the fuel gauges are usually worthless below 1/2 tanks.

So what gives here - & why is this narrative is typical. 

159 Piper Pa28's & 18 Fatalities as a Result of Fuel Starvation

No AD's ........ No Action items - 

Is the FAA and NTSB doing their job or are they just on their way to the crash site to investigate,  According to the NTSB, why bother.

"I think that there are things that should never happen, really the easy things...," NTSB Chairperson Hersman said. "And I think that among the things in the bucket that are easy ... fuel starvation. How many times do our investigators need to investigate an accident like that."

Press Coverage of NTSB Chairperson Barbara Hersman 

If they do look and check,  chances are they would find a fuel sender like this one - and wonder why this belongs in an airworthy aircraft.

Fuel Management

Fuel Management

“From an accident prevention perspective, fuel mismanagement is one of the most frustrating problems. The accidents are easy to avoid. The hardpart is reaching the pilots who are most at risk, because they’re not the ones attending safety seminars or taking online courses. A new approach is needed to get pilots to stop and think about the issue. Airing some ‘dirty laundry’? Perhaps, but we think it’s more than justified by the lives, aircraft, and dollars we lose to this problem every year. 

ACCIDENTS do far more damage to GA’s reputation than educational efforts to rectify the situation.

It shows that, the pilot community,  is making a good faith effort to address the problem.”

—Bruce Landsberg, President, AOPA Foundation

Fuel Management Accidents

Fuel management accidents are among the most preventable types of GA mishaps, and yet pilots still manage to turn perfectly good airplanes into impromptu gliders at an alarming rate well over two per week in the US.

The primary way GA pilots manage fuel on board is to do arithmetic.



 You look at the length of your trip, the winds, read some performance charts, then bust out your calculator or whiz wheel  to figure out how long it will take you to get to your destination at what fuel burn. I might get anywhere from 10 to 18 miles per gallon on a flight. And if the headwind is stronger than I expected or I'm routed the long way, it might take more than that. The 30 minute required reserve  is really not enough. 

FAR Part 91-151

Why Don't They Just Fix It

What is the Aviation Market for Fuel Level Sensing Technology

• Fuel Level Sensing is a very large market for other vehicle types or stationary fuel storage, aviation is a minuscule percentage of sales.

• The following companies are big players in these markets and are protective of their market share:

• Textron Kautex      -TI Group
• Wallbro                  - Robert Bosch
• Hyundai Mobis      - Delphi
• VDO                      - Toyota
• Bourns                    - Methode  
• Rochester Gauge    - Wema, Isspro, S-W

• Most of these companies are not interested in or will actively avoid the aviation market 
• Business interest to license is minimal and no interest in government controlled production
• Exposure to litigation  

• Fuel Level Sensor industry is protective of its Intellectual Property. 

• Hotly Contested Territory (It has been termed a patent minefield) 
• A thorough  patent search is required, prior to initiating a design process.
• Interest in sharing and licensing intellectual property is limited at best.

• Fuel Level Sensing in aircraft needs to be "Intrisically Safe".

• Explosion Proof 
• Limited Spark or Heat energy in the fuel tank
• TWA 800 Disaster brought about changes in FAA policy / regs.
• SFAR 88 - Wire separation from fuel system.
• Electronic Wiring Inspection System - EWIS.  

• Fuel Level Sensing in aircraft is complex. 
• Fuel can contain dissolved air - ie. Jet A 14% by volume 
• This will outgas like soda at altitude.
• This will influence simple capacitive level systems
• Aviation fuel will contain water
• The changes in altitude due to descent will suck ambient air into the fuel tank, that air will contain water vapor that will condense and mix with the fuel. 
• This will  influence simple capacitive level systems
• Aviation fuel will support biological growth and water in fuel will initiate corrosion
• Metallic or resistive components in the tank will be adversely effected and fuel level output in turn will be adversely effected.
• Fuel in aircraft is more dynamic.
• A vehicle with three dimensions of motion allows for a very dynamic fuel environment. 
• This movement will wear away resistance senders of all types and require mechanical complexities to capacitive sensors to stabilize the local fuel level.
• Replacements to 100 LL Avgas may not be so friendly to existing resistance senders in the fuel tank.

• Non-Contact Fuel Level Sensing, which meets the requirement for "Intrinsically Safe" is actively pursued and "IP" accumulated in the Fuel Sender Industry for functional and business reasons.

• Current best sensor system for Multi-Fuel vehicles
• Best sensor system for 100% alcohol fueled vehicles 
• Solves issues with partial alcohol content - corrosion
• Solves issues with de-sulfered diesel 
• Required for LNG -  LPG
• Future vehicle systems with long term fuel storage i.e.. Chevrolet Volt

• Aviation specific fuel system suppliers are not actively interested in the Non-Commercial, Non-Business aircraft application of their products or product lines.

So designing, building and certifying an aviation specific fuel level sender for aircraft under 12,500 lb is like most things in aviation. difficult, challenging and more involved than a cursory examination suggests.   It was however, not impossible.