182 down by Smithers

[pelmet]

Why do you recommend opening the throttle?

Best explained in this article here with no clear answer as to why......

https://books.google.ca/books?id=1bkFXh ... ce&f=false

I remember way back in the day when Raf Zur blew a tank on a 185 in the circuit in Langley, switched, got nothing, and continued to the flare with the throttle wide open. As he was about to touch down, the engine finally fired, at full throttle, and more or less twisted out of his hands enough to hook a wingtip and bend the thing.

Obviously, the full engine shutdown procedure had not been performed and the mixture was still rich.

[ahramin]

In what other situations would you advocate deviating from manufacturer published procedures?

Lol. If trimming for 70 kts, turning towards a landing spot and pulling the prop full coarse are deviations from the above procedure, what's your plan for getting it on the ground following the checklist?

I suspect the difference in glide between full fine and full coarse in a single engine piston prop with a dead engine is negligible.

There is a reason why it is not in the published procedure.

It doesn't make a difference. Most pilots can process information at 70 knots.

Follow the manufacturer's published procedure.

Always good advice Telex. Perhaps you'd share a bit more advice with us: If I'm cruising with the prop control at low RPM, would leaving it there be a deviation of the manufacturer's published procedure or should it be returned to full fine? Not to put too fine a point on it, the reason Cessna does not include the prop control in the checklist is not because it's vital to leave it exactly where it randomly happens to be, but for the same reason they do not include the yoke in the checklist: certain controls can be left to the pilot to decide what to do, while others must be set in a specific manner. The ones that must be set in a specific manner are the ones in the checklist.

As for the difference in glide being negligible, if that's the case why do you consider it so important not to touch it? In the aircraft I was testing last month however, the glide went from 1.4 nm / 1000' with the prop full coarse to 1.2 nm / 1000' full fine. When crossing the water from Vancouver to Vancouver Island the worst case glide to get to land is 5.5 nm. At the normal Westbound crossing altitude of 4500' full coarse gets you 6.3 nm while full fine leaves you just a little short at 5.4 nm. Just the way the math happens to work out for our particular situation here in BC but I don't consider the difference between shoreline and swimming negligible.

[pelmet]

I suspect the difference in glide between full fine and full coarse in a single engine piston prop with a dead engine is negligible.

Unfortunately, you don't provide any evidence, just a suspicion. As we have seen with airliners, the manufacturers procedure isn't always foolproof. And not one POH for singles recommends going to fine pitch from cruise power, just nothing mentioned.

Here is a link to a very good book about propellers.

http://dl.booktolearn.com/ebooks2/engin ... s_89bb.pdf

"In the event of an engine failure, the prop will reduce speed
to around 1200 RPM as it windmills. The power required to
cause the prop to windmill is provided by the free air stream
flowing through the prop disc. In an attempt to maintain
RPM, the CSU will decrease the blade angle to the fine/flat
pitch stop. However, a windmilling prop produces more drag
in fine/flat pitch than it does in coarse pitch. Therefore, on a
single-engine aircraft select full coarse pitch before the engine
stops running. The required oil pressure to the CSU piston will
be lost once the engine has stopped and then it is too late to
select coarse pitch. Reduced prop drag improves the aircraft’s
glide ratio enabling it to cover a greater distance in the ensuing
forced landing."



Select coarse pitch after a power loss in a piston single with a constant speed prop if you want to extend the glide range. It may save your life.

[telex]

Lol. If trimming for 70 kts, turning towards a landing spot and pulling the prop full coarse are deviations from the above procedure, what's your plan for getting it on the ground following the checklist?

I suspect the difference in glide between full fine and full coarse in a single engine piston prop with a dead engine is negligible.

There is a reason why it is not in the published procedure.

It doesn't make a difference. Most pilots can process information at 70 knots.

Follow the manufacturer's published procedure.

Always good advice Telex. Perhaps you'd share a bit more advice with us: If I'm cruising with the prop control at low RPM, would leaving it there be a deviation of the manufacturer's published procedure or should it be returned to full fine? Not to put too fine a point on it, the reason Cessna does not include the prop control in the checklist is not because it's vital to leave it exactly where it randomly happens to be, but for the same reason they do not include the yoke in the checklist: certain controls can be left to the pilot to decide what to do, while others must be set in a specific manner. The ones that must be set in a specific manner are the ones in the checklist.

As for the difference in glide being negligible, if that's the case why do you consider it so important not to touch it? In the aircraft I was testing last month however, the glide went from 1.4 nm / 1000' with the prop full coarse to 1.2 nm / 1000' full fine. When crossing the water from Vancouver to Vancouver Island the worst case glide to get to land is 5.5 nm. At the normal Westbound crossing altitude of 4500' full coarse gets you 6.3 nm while full fine leaves you just a little short at 5.4 nm. Just the way the math happens to work out for our particular situation here in BC but I don't consider the difference between shoreline and swimming negligible.

Do you think there might be a better flight planning option available to you in such a scenario?

Or are you so confident in your coarse pitch glide ratio that you will walk the fine line between landing or swimming?

[telex]

I suspect the difference in glide between full fine and full coarse in a single engine piston prop with a dead engine is negligible.

Unfortunately, you don't provide any evidence, just a suspicion. As we have seen with airliners, the manufacturers procedure isn't always foolproof. And not one POH for singles recommends going to fine pitch from cruise power, just nothing mentioned.

Here is a link to a very good book about propellers.

http://dl.booktolearn.com/ebooks2/engin ... s_89bb.pdf

"In the event of an engine failure, the prop will reduce speed
to around 1200 RPM as it windmills. The power required to
cause the prop to windmill is provided by the free air stream
flowing through the prop disc. In an attempt to maintain
RPM, the CSU will decrease the blade angle to the fine/flat
pitch stop. However, a windmilling prop produces more drag
in fine/flat pitch than it does in coarse pitch. Therefore, on a
single-engine aircraft select full coarse pitch before the engine
stops running. The required oil pressure to the CSU piston will
be lost once the engine has stopped and then it is too late to
select coarse pitch. Reduced prop drag improves the aircraft’s
glide ratio enabling it to cover a greater distance in the ensuing
forced landing."



Select coarse pitch after a power loss in a piston single with a constant speed prop if you want to extend the glide range. It may save your life.

Just nothing mentioned in the POH.

So you are better than the test pilots, engineers, and lawyers that wrote the POH?

Sure, just invent your own procedures.

[cncpc]

Do you think there might be a better flight planning option available to you in such a scenario?

Or are you so confident in your coarse pitch glide ratio that you will walk the fine line between landing or swimming?

Tell us this...have you ever had an engine failure in a single?

[cncpc]

Best explained in this article here with no clear answer as to why......

https://books.google.ca/books?id=1bkFXh ... ce&f=false

I remember way back in the day when Raf Zur blew a tank on a 185 in the circuit in Langley, switched, got nothing, and continued to the flare with the throttle wide open. As he was about to touch down, the engine finally fired, at full throttle, and more or less twisted out of his hands enough to hook a wingtip and bend the thing.

Obviously, the full engine shutdown procedure had not been performed and the mixture was still rich.

Raf was the aviation version of Donny Trump, convict elect.

[telex]

Do you think there might be a better flight planning option available to you in such a scenario?

Or are you so confident in your coarse pitch glide ratio that you will walk the fine line between landing or swimming?

Tell us this...have you ever had an engine failure in a single?

Get lost.

[photofly]

"In the event of an engine failure, the prop will reduce speed
to around 1200 RPM as it windmills. The power required to
cause the prop to windmill is provided by the free air stream
flowing through the prop disc. In an attempt to maintain
RPM, the CSU will decrease the blade angle to the fine/flat
pitch stop. However, a windmilling prop produces more drag
in fine/flat pitch than it does in coarse pitch. Therefore, on a
single-engine aircraft select full coarse pitch before the engine
stops running. The required oil pressure to the CSU piston will
be lost once the engine has stopped and then it is too late to
select coarse pitch.

That doesn't sound right. As long as the prop is turning, so is the engine-driven oil pump, so there should be no loss in oil pressure; and anyway, the oil pressure to drive the propellor off the fine stop is provided by a high pressure oil pump in the CSU, which is also turning as long as the prop is turning. So whatever prop control you have at windmilling rpm is independent of engine power.

[ahramin]

Telex if it makes you feel any better, it happens that the pilot who taught me to pull the prop control out for best glide IS a Test Pilot School graduate and DID write the checklist on a few single engine aircraft. As you say, these people are the experts and their advice is usually best followed.

No one here is arguing that we know better than Cessna. Pilots need to be familiar with the aircraft POH and need to follow the checklists. That doesn't mean that the checklists contain the totality of techniques and knowledge necessary to operate the aircraft. Crosswind landings would be difficult otherwise.

[ahramin]

"In the event of an engine failure, the prop will reduce speed
to around 1200 RPM as it windmills. The power required to
cause the prop to windmill is provided by the free air stream
flowing through the prop disc. In an attempt to maintain
RPM, the CSU will decrease the blade angle to the fine/flat
pitch stop. However, a windmilling prop produces more drag
in fine/flat pitch than it does in coarse pitch. Therefore, on a
single-engine aircraft select full coarse pitch before the engine
stops running. The required oil pressure to the CSU piston will
be lost once the engine has stopped and then it is too late to
select coarse pitch.

That doesn't sound right. As long as the prop is turning, so is the engine-driven oil pump, so there should be no loss in oil pressure; and anyway, the oil pressure to drive the propellor off the fine stop is provided by a high pressure oil pump in the CSU, which is also turning as long as the prop is turning. So whatever prop control you have at windmilling rpm is independent of engine power.

It does seem to mix up multi and single engine propellers. How does the engine turn at 1200 rpm if the prop is stopped?

[Cliff Jumper]

Therefore, on a single-engine aircraft select full coarse pitch before the engine stops running. The required oil pressure to the CSU piston will be lost once the engine has stopped and then it is too late to select coarse pitch.

perhaps that quoted person meant 'turning' not 'running'.

[cncpc]

Do you think there might be a better flight planning option available to you in such a scenario?

Or are you so confident in your coarse pitch glide ratio that you will walk the fine line between landing or swimming?

Tell us this...have you ever had an engine failure in a single?

Get lost.

The question is are you lost?

You're on here running your gob at other pilots about manufacturer's recommendations, and I'm sure I'm not the only one here thinking "Has this fecker ever actually had an engine failure"? So, it being in my nature to ask possibly uncomfortable questions, I asked you if you had. You popped your own bubble with that response.

Because if you had, you'd have some idea of the mental processes you go through. You'd know that while it may be incorporated in your drills, you don't specifically wonder "Would the manufacturer approve of this"? You are trying to keep yourself and your passengers from harm. The manufacturer is trying to protect itself from legal liability. With that in mind, it will say only the minimum necessary. Saying the wrong thing in a recommendation can open it up to damages. You're never going to see a manufacturer recommending something that has its basis in tradecraft or individual pilot experiences, or learned airmanship.

The manufacturer tells you the best glide speed and it sets out a restart procedure which may include positioning the prop control, if there is one. It sets out a procedure for securing the aircraft as best as possible, i.e. preventing fire in the crash sequence, preventing door jambs, making sure safety belts are on. But it is never going to tell you everything to do in any given situation. It doesn't tell you how to stretch your glide, as it doesn't tell you to sideslip first before going to flaps if you are high in any portion of the approach. It doesn't recommend the flight school figure 8 approach or the high key, low method. That is up to you. If you believe you may be falling short of some sort of safe harbour or the least worst place to start bumping into things, and you have good reason to believe that setting a variable pitch to a certain setting, or stopping the prop altogether, may allow you to extend the glide to where you want to come to earth, you don't need manufacturer's approval to do that.

I do think that with the variable pitch prop scenario, you'd want to know the correct answer to that. This is about a accident in a single, and this question really only comes up with singles. For obvious reasons, more complex issues arise in a twin side by side, and the only option is feather the failed one. The reason being, I'm told, is that a windmilling prop provides the same drag as a solid disk of the same diameter as the prop. If that is true, it is also true on a single. You can't feather most singles, but you can stop every prop by raising the nose and lowering the speed.

You will glide a bit farther doing that.

If you wonder why I asked you the question, consider this. Ask any person flying in small aircraft regularly enough that they come to contemplate what will happen if an engine stops, if they would want to have someone at the controls who had never had an engine failure, or someone who had. Nobody is going to say "Sure, she survived, but did she follow the manufacturer's recommended procedures?"

That's why I asked you. Not everything is learned in a book.

[photofly]

I tried pulling the prop control fully out in a power-off glide, and as slow as the engine was already turning, the RPM did drop by about another 100. So that would suggest it would decrease the rate of descent. I'll add it to my list of things to do in a forced approach scenario.