당신은 주제를 찾고 있습니까 “p leads aviation – Aircraft Magneto P-Leads — Three Types“? 다음 카테고리의 웹사이트 https://chewathai27.com/you 에서 귀하의 모든 질문에 답변해 드립니다: https://chewathai27.com/you/blog. 바로 아래에서 답을 찾을 수 있습니다. 작성자 Bogert Aviation 이(가) 작성한 기사에는 조회수 35,976회 및 좋아요 95개 개의 좋아요가 있습니다.
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d여기에서 Aircraft Magneto P-Leads — Three Types – p leads aviation 주제에 대한 세부정보를 참조하세요
P-Leads are critical to aircraft safety. The P-Lead is the shielded wire that connects the magnetos to the mag switch in the cockpit. If this wire breaks, the ignition may always be \”HOT\” with the engine ready to fire. This is extremely dangerous for anyone moving the propeller even a little bit. If this lead shorts to the engine or airframe or shorts between the center conductor and the shielding, the ignition will be \”KILLED\” and the magneto will not work. Either way, it’s a bad situation. Replace worn P-Leads with new if the shielding is frayed or the insulation is cracked. Richard Bogert talks about the three main types of P-Leads commonly found in service on Bendix and Slick style magnetos and how to tell them apart. Thanks to Quality Aircraft Accessories for some of the magneto images.
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P-Leads – Aircraft Spruce
Magneto P-Lead Adapter (S200 S600 Later S2 S4 S20). $37.95. Quick Shop. product_image. Bogert Aviation Slick Style P-Leads. From $53.00 to $100.00.
Source: www.aircraftspruce.com
Date Published: 12/5/2021
View: 5319
How It Works: A pilot’s guide to magneto P-leads – AOPA
The “P” in P-lead comes from the primary winding in the magneto’s coil. To deactivate the magneto, the primary winding is grounded. An ignition …
Source: www.aopa.org
Date Published: 1/30/2021
View: 7631
P-Leads from Aircraft Spruce Europe
P-Leads. Engine-Parts_Magnetos—Parts_P-Leads. P-Leads. = Delivery in 1 day. = Delivery in 3-10 days. = Delivery in 10 days. = Unknown (3 weeks or more) …
Source: www.aircraftspruce.eu
Date Published: 3/20/2021
View: 9717
P-Lead – Aviation Glossary
Primary lead. The wire that connects the primary winding of a magneto to the ignition switch. The magneto is turned off by grounding its P-lead.
Source: dictionary.dauntless-soft.com
Date Published: 6/6/2021
View: 5998
Pesky “P” Leads – Tennessee Aircraft Services, Inc.
The purpose of the “P” lead is to disable the output of the magneto by shorting its primary coil to ground. The three most likely failure modes …
Source: www.tennesseeaircraft.net
Date Published: 11/15/2021
View: 2638
P-Leads – Pilotshop
Magneto P-Lead Adapter (S200 S600 Later S2 S4 S20). $37.95. Quick Shop. product_image. Bogert Aviation Slick Style P-Leads. From $42.95 to $90.00.
Source: www.pilotshop.com
Date Published: 3/10/2021
View: 9363
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- Author: Bogert Aviation
- Views: 조회수 35,976회
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- Date Published: 2012. 11. 26.
- Video Url link: https://www.youtube.com/watch?v=D-GBt_4dvf4
Aircraft Spruce
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How It Works: A pilot’s guide to magneto P-leads
Pilots can get a lot of ideas, both good and bad, by attending the hangar flying sessions that occur in the local pilot lounge. These are also some of the biggest values in airport entertainment.
P-Leads (click on image for slideshow)
During a recent gathering, the discussion involved magneto P-leads, the small wires that start at the magnetos and seem to disappear into the firewall. A local aviator suggested that if he had to make an emergency departure in his trusty flying machine without his ignition key, he would simply cut, or disconnect, both P-leads. He claimed this procedure would render his magnetos hot and it would be a simple matter of starting the engine by hand.
A qualified technician provided some additional considerations, but his comments were met with “deer in the headlights” stares. It appeared the average pilot may be missing a rudimentary understanding of magneto P-leads.
A student pilot learns that magnetos are driven by the engine and operate independently from the electrical system (see “How It Works: Magneto”). A spinning magnet induces a large current and small voltage in the primary winding of a coil. A secondary winding then develops a small current and a large voltage which is then routed to the spark plugs. Even if the aircraft generator and battery experience failures, there should always be dependable ignition. But, a way to shut off each of the magnetos is required. That’s where the P-leads come in.
The “P” in P-lead comes from the primary winding in the magneto’s coil. To deactivate the magneto, the primary winding is grounded. An ignition switch opens and closes the P-lead circuits to a suitable ground. The internal workings of an Off/R/L/Both ignition switch contain the required connections. When selected to OFF, both left and right P-leads are grounded and both magnetos are off. In the LT position, the right P-lead is grounded. The RT position grounds the left. In Both, both P-lead circuits are open, and both magnetos are on. Without P-leads, both magnetos would be hot at all times.
Some ignition switches have a Start position. If one of the magnetos has an impulse coupling or an induction vibrator, typically the left, the engine is started on that magneto. The Start position is identical to having the switch selected to the LT position and includes powering the starter. Some magnetos have two P-leads with two independent sets of points, known as retard and advance. The Start position utilizes the retard points. After starting, with the switch in Both, the advance points become active. A starting induction vibrator is used to create a continuous spark for the retard points, and requires its own electrical power source.
If possible, the P-leads should be visually checked for fraying, chafing, or other damage during preflight. Damage along their length, or a short to aircraft structure, can render the magneto erratic or uncontrollable. Also, running functions of the P-leads should occasionally be checked. Prior to engine shutdown, at idle RPM, position the ignition switch to OFF. When the engine RPM is clearly decreasing, return the switch to Both. But, if the engine continues to run, at least one of the magnetos is still on. This is a dangerous situation wherein the engine could start by simply moving the propeller, and should be addressed by a maintenance technician.
Now, it’s back to our intrepid aviator who is planning his great escape by cutting or disconnecting his P-leads. To be successful, he would need easy access to the back of both magnetos, which is not often possible depending on cowling design. There would have to be at least one impulse coupling. Also, some magnetos have a large nut which disconnects the P-lead, and some connectors of this type have a safety feature that renders the magneto inoperative if unfastened.
If both magnetos are somehow rendered hot, there is the distinct possibility that during manual engine rotation an impulse coupling magneto, with its retarded spark, could induce a sudden engine start. The other hot magneto, with the advanced spark, could create violent backward rotation. Engine damage and personal injury are likely.
Any attempt to start an aircraft engine by bypassing safety features, including the ignition switch and P-leads, could be a very expensive and extremely dangerous procedure, and should never be attempted. The best advice is to learn all you can about your particular aircraft and operate it in strict accordance with the manufacturer’s instructions. Oh, and keep a spare ignition key in a handy location.
Aviation Glossary
Aviation Glossary :: P-Lead Welcome to the Dauntless Aviation Glossary! At Dauntless, our editorial staff maintains the web’s largest unified glossary of aviation terms. This glossary is built from a combination of official, quasi-official, and proprietary sources (including original material that we develop oursselves). Uniquely, we often provide multiple definitions of a given term so that you can find that which best applies to you. In order to maximize your learning efficiency, this glossary (and similar ones for our international users) is incresingly fully integrated into our aviation learning apps, including our FAA written test prep and FAA practical test prep software and apps. If you like this glossary, you’ll love them with their polished learning environments and world’s best and clearest content (please do give them a try.). P-Lead P-Lead
Terms and Definitions P-Lead
Request a Term P-Lead Primary lead. The wire that connects the primary winding of a magneto to the ignition switch. The magneto is turned off by grounding its P-lead. source: FAA Aviation Maintenance Technician Powerplant Handbook (FAA-H-8083-32)
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Pesky “P” Leads
Pesky “P” Leads
Pesky “P” Leads
Our Cessnas are designed with certain redundant systems; two fuel sources, back up electrical source (battery), dual magnetos, etc. Each redundant system has some area of common connection or weak point that must be carefully maintained to ensure the reliability of the entire system. Often the weak point is some very simple item that rarely gets much attention during inspections. Magneto “P “ leads are very simple pieces of wire but have the capacity to ruin your entire day when they fail.
The purpose of the “P” lead is to disable the output of the magneto by shorting its primary coil to ground. The three most likely failure modes of the “P” lead is a short to ground, an open, or intermittent between grounded or open. A short to ground will totally disable the magneto. An open allows it to fire any time the magneto is rotated which is a particular danger if the prop is rotated by hand for some reason. An intermittent short or open not only creates operating problems but seriously messes with a mechanic’s mental stability. Prevention of these three possibilities is not difficult but does require just a little special information.
When the ignition switch is in the “BOTH” position the “P” leads are effectively disconnected from the magnetos. While in this condition, some of the coil energy rides on these “P” leads to the tune of about 150 volt pulses. These voltage pulses occur every time the magneto fires and are used by some digital tachometers to generate RPM displays. A four cylinder magneto fires twice per engine revolution, and a six cylinder fires three times per engine revolution; the digital tachometer merely does the math and puts up the appropriate display.
The pulsating direct current on the “P” leads effectively becomes alternating current without the negative pulses when the engine is running at cruise speeds. A six cylinder magneto running at an engine speed of 2700 revolutions per minute translates to 8100 pulses per minute or 135 per second. This relatively high frequency and high voltage will wreak havoc on avionics audio systems and Automatic Direction Finders (ADF). Shielding the “P” lead wire is the remedy.
Shielded wire is a standard insulated wire with a braided wire wrapped around it. Usually another layer of insulation is added outside of that to protect the shield. Antenna coax is a type of shielded wire intended to protect its carried signals from outside interferences. Strobe systems often use a shielded wire from the circuit breaker to the power pack for noise suppression. Audio wires use shielded wires and should have all the shields grounded at the same point for best effectiveness.
One unique feature of the “P” lead is that most of it is exposed to the harsh environment of the engine compartment, complete with major temperature swings, oils, cleaning solvents, and vibrations. Of all the wires in the plane, the “P” lead probably gets disconnected and re-connected more than any other wire. All this translates to excessive wear with need for more care during maintenance and close attention during inspections.
Avionics guys/gals deal with shielded wire every day and have all sorts of special tools and tricks just for them. Your local mechanic so seldom has to repair or install shielded wire, he/she may not be well versed in the various common failure points or repair methods. The most common fault is a broken shield lead at the magneto which can totally negate the electrical noise canceling ability of the shield. It’s also commonly ignored due to lack of knowledge of appropriate repair methods.
When inspecting the “P” leads at the magneto end one should look for frayed strands on the grounding braid. These very small wire strands must be twisted together for support or they may break easily. To expose the wires’ center conductor for detailed inspection, the braid should be pushed up the center wire like pushing up the sleeve of your shirt. The center wire insulator often gets thin and cracks at this point allowing the high voltage spike to arc to the shield. Any evidence of cracks in the insulation or dark spots indicating arcing is cause for repair. Repair of a damaged “P” lead requires cutting off the offending damaged length, then separating the shield from the center conductor and attaching each to the appropriate post on the magneto.
One repair option is to install a pre-made heat shrinkable device with a ring of solder and a grounding lead built in. The wires’ outer insulator is trimmed away about two inches from the end using a fresh razor blade. The blade is pressed through the insulator until just touching underlying braid. A sawing motion with the blade will score the braid causing many strands to break. The braid is then cut about 1/8 inch from the new edge of the outer insulator using the same method with the razor blade. Care must be taken to prevent cutting into the inner wires’ insulator. The narrow ring of exposed braid is the contact point for the solder ring of the heat shrinkable part to melt into. Terminal ends are then crimped on the newly installed ground wire and the center “P” lead.
Another repair method involves no special tools other than soldering tools and a proper pick. As in the previous procedure the outer insulator is trimmed off about two inches from the end of the wire. The shield is pushed up the wire creating a bulge in the shield near the freshly cut edge of the outer insulator. Using the pick, carefully create a hole in the braid. Slowly bend the wire away from this opening as you continue to enlarge it. Eventually, the wire will be bent 180 degrees and the center wire can be pulled through the opening. The braid can now be pulled and twisted to create a strong conductor for the ground lead. Added strain relief can be had by adding short bits of heat shrink tubing where the braid now departs the center wire.
Wiring repair is not on the list of items the FAA says the owner/operator can do. However, when you have the cowling off for that next oil change or spark plug cleaning the “P” leads could certainly get a looking over. Look for frayed shield braid and give a gentle tug on the wire at the terminal end just to ensure it’s connected well. Care for “P” leads is truly an ounce of prevention returning a pound of cure.
Copyright © Paul New 2010. All rights reserved.
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