Armstrong

From DH82.com
Jump to: navigation, search
Alt text
Ever has it been so...

Prop-swinging:

The mere mention of which is enough to strike fear unbridled into the hearts of the uninitiated and spark endlessly rabid debate in online forae amongst those both pro- and against this ancient art. Hand-swinging an aircraft used to be so commonplace as to be utterly unremarkable. Even today some of the more "vintage" types still flown, must be swung to start -they have no electrical system. Starting a reciprocating engine today is still just a technologically-advanced variant of handswinging... give it a little thought perhaps. Self-sustaining suck, squeeze, bang, blow is still the desired end-result. The engine is still started today primarily because a force is exerted (by whatever means) that leads to rotation of the crankshaft. Whether that force is applied by turning a key, flicking a switch or swinging a prop, the end result is the same. The engine starts[1].

Respect

ALWAYS treat every prop as LIVE, all the time, EVERY time, unless YOU have PERSONALLY proven it dead. Lots of emphasis, I know -but your life may depend on it. The only way I know of to prove an operational engine/prop dead is to conduct a proper mag function/dead-cut check yourself prior to shutdown. Only then can you be sure... to a degree. Hotspots within the engine may obviate a proven dead mag, allowing the engine to fire, however briefly. It doesn't take much to kill you. Respect EVERY prop.



Armstrong Starting:

Like everything else, there is a right way and a wrong way to go about achieving the desired end-result -a happily running aircraft engine. Almost inevitably, for as many different aircraft types as there are in existence, there are almost as many different right ways of hand-starting them. What is right for this airframe and engine, will be very wrong for that airframe and engine... know your airframe, know your engine, know the correct technique. Because there are so many airframe/engine-specific variants upon the same theme, this document will not be written as a treatise on how-to-go-about-it, rather a much broader theme, in more general terms that I hope will provide some insight on how to proceed safely, with your aircraft and all your personal "bits" still in prime shape.

It strikes me that it was not too long ago that most -if not all aircraft were started by variants of the Armstrong method -if you want to be really pedantic, they still are!!! We just use electrical and mechanical means today to apply the requisite force to the crank-shaft. We still supply the engine with the fuel, air and ignition support it needs and provide the initial motive force by whatever means we have best available. Suck, squeeze, bang, blow is still the same -we just need to get the process self-sustaining.

In my opinion, it is nonsensical to write-off handswinging as some self-proclaimed "gurus" do. GA is fraught with possibilities for pilots to find themselves in a position where it may be the only practical, realistic opportunity to achieve their mission without major inconvenience, physical damage to an airframe (beach landing, dead battery, rising tide anyone?) or major expense getting a qualified repairer, spares and tools to the aircraft location.

I'm not about to write a treatise here explaining how I do it or how I think it should be done. I am going to repeat what I said earlier: get training!!! Personally I'd tend to chose someone that does a fair bit of it -a Tiger Moth operator, for example. They're a fairly benign aircraft to swing, there's a few of them about, the people operating them are most likely well-practised and have robust, effective systems in-place and the principles you'll learn are in broad strokes applicable to whatever you may have to Armstrong in future, with type-specific variations, of course.

It's not a process conducted solely by Captain Barry Strongjaw types attempting to impress their femme fatales... it's something you need to learn, because the situation may arise at some point that you need to swing an engine. It's a fairly simple, safe process if conducted properly and underpinned by knowledge gained from proper training. Basic Airmanship, really.

Training:

SEEK A KNOWLEDGABLE INSTRUCTOR AND UNDERGO FORMAL TYPE-SPECIFIC or DIFFERENCES TRAINING!!! Especially if:

  • your aircraft is a type which must be Armstrong started,
  • you regularly operate into remote areas, well-removed from assistance to rectify problems,
  • you can envisage a circumstance that you may need to practice an Armstrong start,
  • you have a desire to advance your knowledge of your aircraft and basic Airmanship techniques.

In ALL cases on aircraft that don't rely primarily or solely on this method, the Armstrong start is the method of absolutely last resort, which presupposes all other avenues of safely achieving an engine start (battery cart, jump-start, engineering support etc.) have been exhausted.

The Need:

The very necessity of committing an Armstrong start may arise from a variety of less-than-fortunate circumstances:

  • A flat battery is probably the most common.
  • Your starter Bendix may have "hung-up" (jammed).
  • You may have lost your ignition key!
  • Your key barrel may be worn to the degree of unservicablility.
  • Any number of other issues may lead to contemplation of an Armstrong start.

The Prep:

  • Unless the situation is absolutely desperate, Armstrong starting is always a minimum 2-pilot operation. Think it through thoroughly, set it up carefully, execute the process deliberately. A successful outcome is likely.
  • Know what Magneto's are fitted to your engine! That may sound a little odd... but when conducting an Armstrong start, it will probably make a difference! Briefly, a Magneto can be described as an electrical generator that uses permanent magnets to produce periodic pulses of alternating current. It is categorised as a form of alternator. In aircraft engines, it is what keeps the ignition independent of the rest of the electrical system and ensures that the engine continues running in the event of an alternator or battery failure. For redundancy, virtually all piston engine aircraft are fitted with two magneto systems, each supplying power to one of two spark plugs in each cylinder. Aircraft magnetos are used in piston aircraft engines and known for their simplicity and reliability. Often sold in pairs, or as a dual magneto, this compact device requires no external electrical source to operate. The most common Magnetos are manufactured by Bendix or Slick.
    • Non-Impulse coupled Mags: rare, these days.
    • Impulse coupled Mags: almost ubiquitous now.
    • Shower-of-Sparks Mags: provide more reliable start performance, but do require that the starter be energised (switch selected to START) -or no Shower of Sparks!!!
    • Solid-state electrical systems are fitted to some later engines. I know nothing of those or their performance during an Armstrong start.
  • Restrain your Aircraft!!! Chocks at a bare-minimum, better: a tail-restraint for tricycle or tail-dragger airframes. Use a properly secured picket and rope.
  • The Pilot swinging the Prop has overall Command -and responsibility- for the whole evolution.
  • The Pilot in the cockpit does only what the Command Pilot instructs -no more and no less. No room for individual creative thought here at all.
  • The two pilots need to thoroughly brief the evolution and clearly understand what each will do and how the challenge/response calls to be used will be.

Start!

Once the aircraft is properly secured, the crew prepared and the engine set-up as far as is possible, it's time to get on with it[2]

Proceed as is appropriate for your aircraft and engine, in accordance with the training you have received!

Notes

  1. I have Never heard of anyone enjoying success trying to Armstrong start a Gas Turbine... but by all means, have a go! There's got to be a 1st time for everything. ;-)
  2. Armstrong HOT Starts on any engine are going to be more difficult (Because the engine is hot!), than a Cold start. On a big-bore Lycoming or Continental, it may prove well-nigh impossible.
Alt text
Don't let This be Your result!