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Into wind for run-ups?
Thanks to everyone who contributed to the debate on whether to lean the mixture on the ground; I was amazed at the amount of posts which said to me that the basics aren't being taught at some schools. Now a question on another practice which is being taught differently depending on the training provider...
I was taught that parking into wind for the engine run-ups wasn't necessary and there was no discernable benefit. At other organisations I have flown at, even at the same GAAP, parking into wind was a rule which is written in stone. What were you taught? |
this is an interesting question ! my school taught me to face the wind, power up and then Run up checks....
i am not sure but maybe an instructor can answer that....is it due to more intake of air into the engine ? Richie |
airmanship :-)
........there are a few variables with regards to whether or not it's prudent to face an A/C into wind for any type of engine run ups. The wind strength would be one, if the breeze is light there would be no real advantage as to which way you face the A/C but if it where rather windy then it's good airmanship is nothing else to do all run ups into wind to keep the airflow doing it's best to keep an engine within it's temp limits, (esspecially turbo models) afterall that's the single biggest reason as to why it's taught that way (mostly ) in the first place, for efficent engine cooling under high power settings whilst stationary.
The other consideration is to point an A/C into wind in order to keep the controls surfaces from bouncing around off their stops, less damage in the long run besides at times the control column can bounce around like a miss guided crazed kid behind his dads car steering wheel causing some bruising to the hapless pilot all the while pushing & pulling at various engine controls within the cockpit:-) At the end of the day consider those around you for any engine runups as well as the engine itself. The amount of times i've seen/heard a pilot run up an engine within very close proximity of another causing , that's airmanship. Capt Wally:-) |
for efficent engine cooling under high power settings whilst stationary. The into wind position is going to be most benificial at low power settings, where the airflow through the prop is going to be minimal. All the control surfaces being into wind is also a valid reason, as they are designed to have airflow going over them from one direction. |
Geez it's amazing the crap that's being taught in flying schools these days. I guess you have to expect that if you take a sprog CPL give him an instructor rating and make him think he's Gods gift to aviation when in reality he/she knows squat!
Cooling airflow through the cowl as someone said is going to be handled by the spinning propellor. Controls may blow around in the wind but you should be able to prevent that through the yoke, use the gust lock if you have to. OK Boys and girls, the real reason for pointing into the wind is that if you park in a tailwind with the engine(s) running you can guarantee that the prop(s) will pick up any debris that's on the ground near it causing damage. sigh |
Some of the rules "cast in stone" are carryovers from the time when flying was mainly in taildraggers. Into wind is *always* a good idea in taildraggers.
With tricycle gear, there is less trouble of course with cross/tailwinds, but rather then have to concentrate on holding or stabilising bucking controls when doing run ups, into wind is sensible in stronger and gusting winds. Of course the other oldie is "never taxi faster than a brisk walking pace", I understand mainly derived from the days when a wingman physically walked beside the aircraft and stabilised the wing of the early light taildraggers in gusty conditions. If we all taxied at a walking speed of about 5 km/hr it would take 12 minutes to taxi 1000m, at 10 km/hr about 6 minutes - fun backtracking delays on a lot of runways!!!! It's probably still trotted out to slow down newbies from taxying faster than they can coordinate the pedals..... |
I've just checked what Mr Google says about this ... engine cooling seems to be the consensus as to why run-ups should be done into wind.
http://4vfr.com/?goto=view_article&s...rticle_key=118 http://www.oaafly-in.com/oaawebsite85e/11ACPOM.htm http://www.ufly.com/lessons/ground_operations.html BTW, at 'busy' airfeilds without designated run-up bays, where's the best place to do the run-ups? |
Parking a turbo aircraft into wind after shutdown is a great idea too :ok: not just for the benifit for the flight controls.
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...........excellent reference from what "training wheels" posted here seems that most agree facing into wind is about engine cooling of some discription & seeing as it's a good place to start such a habbit then it will benifit when & if that pilot goes on to fly turbines where into wind (where possible) is very much encouraged for a cooler start process, & as we all know (kero burners) it's the start process of a turbine engine that has the most long term effect on wear & tear................do it now & reap the bennifits by way of good airmanship for latter also.
...........yes one could install the gust lock to prevent controls from being buffeted around during an engine run up in windy conditions but is it not wise to remove such a devise before one even entertains the idea of flight, & that starts as we move the wheels !:-), besides some gust locks actually mask the magneto switches (deliberately) which are obviousaly needed as part of an engine runup. Re-installing the gust lock could set up a potential hazard far from that of the original subject matter here:-) Capt Wally :-) |
Guys what you will actually find, apart from the stone damage side of things, is that alot of this stuff develops from tail wheel aircraft. Runups into wind helps you keep directional control on the ground at high power settings. It also helps you plant the tail firmly down.
As for engine cooling, many engines do suffer from heat soaking when on the ground. The reason many flying schools teach into wind is because many of there will not have CHT's and therefore it is really hard to judge your engine temp.... similar as to why schools wait for the oil temp to be in the green arc..... is your cylinder head warm enough? So it is prudent for new pilots to enable as much flow as possible, especially when running those before takeoff checks on the hot days. As for being airmanship.. well........................................................ .................................. my two cents |
Engine cooling taken care of by the prop?
Take a look at the shape of the prop blade between the hub and the edge of the cowl...say the first 15- 20+cm...it is round and has no aerodynamic properties. The only air travelling through the cowl when the aircraft is stationary and at higher than idle power settings is that which is sucked through by the venturi effect of air flowing around the cowl and passed the cowl flaps, if fitted. At idle/taxi power settings with the aircraft moving 'at a brisk walking pace' there may be little or no cooling airflow through the cowl. Yes parking into any significant wind will help put more air through the cowl...although I suspect the strength of wind required to actually make a difference might be stronger than you'd want to be flying in in the first place. As to wind effects on controls..ailerons excepted...think about how strong the wind flowing around the airframe from prop blast is at the various power settings is. Even at idle it would be 10kts probably. At typical 'mag check' power settings it would be closer to 30-40 kts. I doubt being parked in a 10 kt tailwind would make much difference. The better question to ask is why pilots park in 'run up bays' to do their engine/prop checks in the first place. I would suggest it is a habit that is formed in the first hours of learning to fly because students are deemed to be incapable of taxiing and doing runups concurrently. That is probably a reasonable premise but at some point in the training perhaps it needs reviewing. It has been over 25 years since I have parked into wind, whether in a runup bay or not, and done a classic runup. The vast preponderance of experienced/commercial pilots do them on the run. This is viewed as less than 'professional' by many instructors but when you think about engine cooling on the ground perhaps getting the aircraft off the ground in reasonably short order bares some consideration. |
The vast preponderance of experienced/commercial pilots do them on the run. And he was the owner of the aircraft. |
Surely its an instrument check to see that the tuft of wool sticky taped to the windscreen is working properly:}
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Chimbu Chuck,
I have to ask the question... if you overheat the brakes during taxi, what will you stop with near V1? Most (not all) brake pads on GA aircraft are tiny... are they going to be effective considering your only taking off once and not doing circuits? Secondly, most pilots I know do their run ups prior to taxiing for their run/charter etc.... first thing in the morning. Runups on the run, especially at night, are often hazardous... head inside / head outside and all that stuff. As for air flow.... just have a good look at your oil temps and CHT's next time you do a stationary run-up. I love the comment to save props, if you have your big hoofs on the brakes are you preventing alot of stone damage? Unless your are taxiing at Vr, then you wont need to worry about the brakes.......:ugh: So where do you do your before takeoff checks... during rotate? :oh: pinky just think... he's the owner.. of course h's not wanting to spend cash. :D He owns the bloody thing |
Who said anything about taxiing against the brakes?
First flight of the day a full mag check and prop check while parked is not unreasonable...provided not parked on gravel and done efficiently...that means quickly...not cycling the props 3 or 4 time for no reason as an example...once is enough, twice is overkill unless the first was sticking. In a twin once through to feather at 1500 rpm is heaps...not sitting at 1700-2000 for several minutes while you check each mag and then cycle the prop to see an RPM drop and then reduce to 1500 rpm for the feather check. All you are doings is heating the engine up and learning not a lot. Every other sector of the day does not require anything...where does it say you need to do a full runup before every flight? Every subsequent flight of the day requires, at most, a quick dead mag check...even that you can do parked just before you shut down...not while taxiing out. Pilots get in the habit of doing the full monty every sector because when they learned to fly they did it every flying lesson. Even first flight of the day I do the checks 'on the run' but I slow down to a crawl on a long straight taxiway and then increase power the minimum amount required, say 1600 rpm, quick mag check and cycle the prop(s) once and then reduce power back to low idle. The aircraft doesn't have time to accelerate much so I don't wear out the brakes...and any forward movement reduces stone damage significantly. There is not a SINGLE stone chip on my Bonanza prop and there never has been. You need to understand also that a mag check done at typical rpms around 1700 shows you NOTHING you wouldn't learn by doing the same check at 1000 rpm. If you want to test your ignition system thoroughly do it in cruise...select L and R and leave it sit for 20 seconds and listen. If everything is good it will run smoothly...if not you may have a magneto problem but more likely it is a plug problem..if you are blessed with an all cylinder monitor and know how to use it you will be able to decide which it is and direct the engineer at the end of the day. If you have a little plug fouling you will be as likely to detect it at 1000 rpm...but if you always taxi leaned you won't get plug fouling. |
I thought that one of the reasons that we cycled the prop to flush warm oil through the engine. What do we achieve by doing this on first startup whilst the engine is still cold? On the same subject I also learnt to warm the engine prior to running up for the mag checks, so again why do this cold?
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It is to replace the cold oil in the prop hub with warm oil from the engine not to 'flush warm oil through the engine'...who said anything about not warming the engine up or doing the runups cold?
Read what is written not what you think is written. |
Park them into wind - The gust front of a thunderstorm will mean you find it where you left it.
Run them up into wind - Avoid stone damage, help cool the engine, help get some cool air circulating through the cabin, dont damage the door you have left open to let some breeze through. Keep the controls into wind when taxiing, take-off and land into wind! Try hot starting some aircraft ie C310 in temps above 40 degree's and you will know that 1-2 kts of headwind might just make the difference. My two bobs worth |
The vast preponderance of experienced/commercial pilots do them on the run This business of a pilot rushing around just because it is a GA aircraft reminds me of a classic example of piss-poor airmanship at Essendon years ago. The RFDS Chieftain this bloke was taxiing had a 137 page roller-blind checklist installed on the coaming. It began with "Gidday." It was night time and raining and as the pilot was manoeuvering out of the RFDS lines he was busy scrolling through his checklist and was quite surprised when his wing tip clobbered another Chieftain. There was no fuss and bother from the chief pilot after all it was "just GA" and these little things happen sometimes. Funny thing was, when the airlines had piston engines you never ever saw a DC4, DC3, Convair, Connies et al doing their engine run-ups while taxiing. The captain would have faced disciplinary action and even termination of employment. As far as flying schools waiting for the oil temp to get into the green range before run, that is no more than a money making exercise. Certainly in the Lycomings in Cessna's in cold weather, the POH advises that the oil temp might not even register on the gauge until the aircraft is airborne. So yet another GA myth is destroyed but still the bogans of this industry believe them. :ok: |
Chuckles on the money as usual!:ok:
At the risk of sounding cynical I find it hard to believe that this sort of question and answer time and associated debate still exists in this day and age of Byronist aviation Nirvana. The Great One is on record as having remedied all needs and deficiencies of 'grass roots' flying training to the Australian public in the CASA Annual Report of 2004/2005 Improved safety in flying training Following analysis conducted within the Office of the Chief Executive Officer in early 2004 of General Aviation fatal accidents for the past decade, CASA identified the need to provide increased support for the flying training industry, particularly as a means of reducing the incidence of uncontrolled flight into terrain. To address this need, CASA has formed a team of flying training specialist inspectors and created the Flying Training Industry Development Programme. In conjunction with the specialist inspectors, this programme will help the flying training industry identify issues adversely affecting flying training standards, and develop initiatives and programmes to address these issues. CASA expects the following safety benefits will be achieved: Training for and standardisation of Flying Operations Inspectors and Authorised Testing Officers will ensure appropriate pilot entry standards are understood and applied in a consistent manner on a national basis. Industry will gain an enhanced understanding of the broader issues surrounding flying training standards and will demonstrate a greater acceptance of their responsibilities to maintain high standards in flying training. By adopting a cooperative and collaborative approach, flying training industry participants will be encouraged to share concerns and issues with CASA and offer partnership-based solutions in a constructive manner. Advice from the industry, combined with implementation of targeted programmes on a partnership basis, will deliver an enhanced overall safety climate in the flying training sector. The Flying Training Role Specialists group was formed following announcements from CEO Bruce Byron that CASA is looking to improve our contribution to the flying training sector, and in the future will work closely with the Flying Training Industry Development Panel. The CASA Deputy Chief Executive Officer and Chief Operating Officer, Mr Bruce Gemmell, has reported that the formation of the team and its role is a good example of a changed approach designed to achieve better aviation safety outcomes. "CASA now has a clearly defined focus on passenger-carrying operations, with flying training a high priority. We can't expect safety at the top levels unless we ensure pilots are being trained and assessed properly right from the start." Both students and experienced pilots rely on the quality of the training they receive to develop the skills and knowledge that keep them and their passengers safe, and making real improvements in this area is the group's major focus. With specialists to be engaged in significant face-to-face contact with all subparts of the flying training industry, the training was designed to enable members to present a consistent, up to date and technically competent face to industry to ensure maximum credibility. Flying training specialist group member Leonard Yates reported that the purpose of the week in Maitland was to standardise the group, ensure their flying skills were current and up to speed and look at how instructors should be trained and assessed. "To do this we flew specific sequences in a Cessna 172, with specialists taking turns role-playing instructors and students. "The ground component of the training involved looking at stalling and circuits in flying training assessment. "We also received refresher training in emergency manoeuvre recovery on a Pitts Special aircraft, including inverted spins and other scenarios an authorised testing officer or flying instructor might find themselves in. "For the group it was refresher training, making sure we are all current and confident in handling these situations. "The outcome from the training was a united view about where we should be going in terms of projecting requirements for authorised testing officers and chief flying instructors. "We worked solidly throughout the week finishing up around 10.30 each night with our laptops around the dinner table. I think I can speak for all of the group when I say that the training was invaluable and it gave us a terrific opportunity to bond as a team." |
You wanna compare a Super Connie to a Baron?:ugh:
Of course they didn't do their runups on the move..because they were incredibly complex compound radial engines..and there were 4 of them.:rolleyes: As far as facing courts martial for reckless, unprofessional behaviour? I would suggest that since the RAAF doesn't operate anything in the same class as a Baron or Chieftian and has only operated SE pistons, in recent decades, in the ab initio stage of training it probably isn't in a position to comment on how they can or can't be operated...and neither would one of their products unless and until he has some direct experience. Your example of the RFDS Chieftain pilot is certainly one of less than great situational awareness/airmanship. Those roller blind checklists are cumbersome to use and far from being the best available single pilot checklist. Night time and raining is a good time to slow down and take extra care...but that doesn't make doing some checks on the move 'unprofessional' always..it just indicates that on a dark night with bad weather and a crowded ramp some common sense might be required...but as we all know common sense is anything but common.:ugh: |
The Pelican to the rescue! :}
Also covers ground leaning..sounds strangely like what CC has been saying all this time. Can't think why! :E |
Who said anything about taxiing against the brakes? |
still crazy Chimbu... I guess we will have to agree to disagree here. In my view the pros far outweight the cons, run up's on the run are more prone to human error and it really doesn't save that much more time or money. As for not touching the brakes.... well I seem to remember taxiing at a reasonable speed to be plainly good airmanship.
I agree you dont need to do an engine run for every flight, but if you feel that confortable in your equipment.. well good luck to ya you crazy dutch bastard :ok: |
Propellors
If you do stationary runups on the gravel strips in central Australia, you will not last long, as you will destroy propellors.
You can see a little "willy willy" sucking up gravel below your prop. If the aircraft is moving, this gets left behind, and damage is much reduced. I once watched a military pilot all but destroy a propellor on a Pilatus Porter by doing stationary runups etc on a gravel patch. He must have had a fuel problem, as he arrived un announced, landed, and requested fuel. We told him that we only had avgas but he elected to take some avgas, so was duly refuelled.(PT6's can use avgas-with limits) We then watched as he started up and we ran for cover as his propellor started throwing stones. He sat there for a lengthy period and went through his check list etc, totally oblivious of the damage that the "pinging" stones were doing to his prop. And this in a taildragger with good prop clearance. Military pilots are good for military things. Roller blind checklists have their place, but also have serious limitations. They can actually be a hazard, if not written properly. Too often their purpose is to protect people who are not in the aeroplane. When the RFDS put the first Kingair in Alice Springs the roller blind checklist was more of a "to do list" It was so long it used to jam. It even had the coffee machine as a checklist item. Things are not always as simple as they seem.(and as they should be.) Sometimes, doing checks on the run is the best way, whether the military do it that way or not. The words "it's only GA" have absolutely no place in aviation. This attitude polutes Australian aviation, and is one of the reasons for the sad state of parts of GA. It must be taken seriously, and done properly. It IS different. |
.........god it's hard to believe the amount of stuff written here about what is essentially good airmanship amongst other things. Sure, do engine runups whilst on the move where practicable but use common sense at all times, if it's anyway risky to do so then simply don't !.........sure do runups tail into wind where appropriate but there's no harm doing it (where possible) into wind, back to good airmanship with controls & engine handling, both of which should be respected well before airborne flight:-)
I'm sure all here have seen it all, poor airmanship, poor decision making etc. We are but human but we can make a difference & we can try to do what we believe is correct at every opertunity but never & I mean never at the expense of common sense..........those two words that will always sustain ones life where all else fails.............happy flying & remember the flying isn't over 'till the hangar doors are closed !:[) Capt Wally :-) |
With the greatest of respect to the skygods here, I wish to point out two things.
1. Since I have not flown a particular aircraft all day, and because the pilot who used it before me might be even more inept than I am, I will conduct a runup check. For example, the previous pilot might not have "leaned aggressively on the ground" and my mag check might indicate a minute or two of aggressive leaning is necessary to clean the plugs. Alternatively, he (or she) might simply have not adhered to the POH and written up the MR and declared the aircraft unserviceable because the mag drops and difference were outside limits. I do not wish to discover this situation in the middle of a takeoff roll. 2. Since I am going to do a runup. it might be useful if my aircraft was pointed in the same direction as other aircraft attempting the same exercise. While it might be pleasant to gaze into the eyes of one or two (OK three or four!) female pilots at YMMB, doing it while standing on the brakes and revving the engine offers scope for a kind of mingling that is not my preferred method.:} |
and my mag check might indicate a minute or two of aggressive leaning is necessary to clean the plugs The longer you run the engine at high power, the hotter the internal temperatures get although the CHT gauge, if you have one, may not show much of a rise. But keep in mind, the hotter the engine, the less power it delivers during take off and if in a twin you have an engine failure at a critical time, the already hot engine that you have beaten to death during its run up - will deliver you significantly less power for single engine climb. Extract from the book "Fly The Engine" by Kas Thomas. Chapter 3, page 41 and 42 on Run-Up's: Quote in part: regarding plug fouling and mag drops: "First use common sense. Try a quick burnoff of the plugs. The key word here, is quick. Don't take all day. Run the engine up to runup rpm, or possibly 100rpm higher, with both mags online, and slowly lean for best rpm. Don't be afraid to lean aggressively, because at runup power your engine is putting out, at best, only about 40% power and at that kind pf power setting you aren't going to hurt anything by overleaning. Leave the mixture at the best rpm setting for about 10 seconds. Lean slightly more until the engine just starts to stumble, then enrichen and recheck the mags. If the "bad" mag still sounds bad and still makes you nervous, by all means taxi back. Don't sit there running up, straining on the brakes, kicking up the dirt with the propeller etc needlessly. If a 10 second burnoff won't do the trick the first time, the odds are it won't work any better the second time. All you will do is overheat your engine. Which brings me to another tip: Always face into the wind for run-up (to aid engine cooling) and open the cowl flaps if any. If there is no wind, taxi to a position downwind of any available aircraft and unless blowing dirt is a factor - face into the other plane's propwash" Unquote. It is common to see pilots running up both engines together in a twin. There is no compelling reason for this and forget the myth about nosewheel assembly twisting. What is the point in banging away at high power on one engine while trying to burn out plugs on the other engine that is being tested? Same applies to prop pitch control exercising. One engine at a time please.. Leave the other engine idling leaned out waiting it's turn to do it's stuff. Stays cooler that way. The cooler the internal temps the better chance of safer single engine performance during take off climb. |
Originally Posted by Chimbu chuckles
(Post 2939852)
There is not a SINGLE stone chip on my Bonanza prop and there never has been
R:cool: |
It is always exciting to watch a 700+hp twin doing run-ups FASTIDIOUSLY into wind, (and often directly across the apron/taxiway) whilst a not so experienced pilot taxis behind in a C152.
I wonder how many of the lovers of the static run-up own the propellors. Karumba is certainly not a bad strip as far as stones are concerned - you need to get out more. |
Originally Posted by Spinnerhead
(Post 2944202)
Karumba is certainly not a bad strip as far as stones are concerned - you need to get out more.
R:cool: |
A37575 - two minutes is poetic licence. More like 30 seconds, and its only on a couple of aircraft that I fly that occasionally get the problem (200HP Lycoming).
On gravel strips of course do a rolling runup. As for only doing first "flight of day" runups, of course do it, presupposing it's an aircraft you are familiar with and nobody else is going to use it except you. If you are hiring an aircraft, as far as I'm concerned its 'caveat emptor". I don't know what the state of the engine is apart from whats written on the MR. Two sentences keep going through my mind: "The engine in this aircraft always does that." "Didn't you know about XXXX? It's been like that for months." Also with the greatest of respect, while I can see the virtues of whats been written in this and the leaning thread. It would be wise for simple people like me and students to think very hard about how to incorporate these teachings into their operations without incurring the ire of their instructors. |
I would suggest that since the RAAF doesn't operate anything in the same class as a Baron or Chieftian and has only operated SE pistons, in recent decades, in the ab initio stage of training it probably isn't in a position to comment on how they can or can't be operated.. Be careful dismissing the experience garnered from those who operate in a significantly different manner to you. You'd be surprised the lessons learned and considered 'common knowledge' on the other side of the fence, just as the military has a lot to learn from us mere civilians.:= |
Round prop hubs
Hey Chimba,
I read Deak's article where he stated the first 20 odd cm of the prop is round and of no aerodynamic value way back when he wrote it. This seemed plain wrong for all the props on flat engines and can be verified by simple observation. Sure it's fat but it is still a good aerofoil. However quite correct for round engines. Since I fly both I went and looked at a few, the 1340, 985 and Dromader donks certainly have round hubs the old Hamilton Standard partcularly. However by the time the hub forms into a workable aerofoil it is at about the same radius as the outer crankcase, the crankcase doesn't need cooling airflow, by the time you radius out to the cylinder the blades are now shaping up just fine, still the cylinders don't need much airflow, get to the radius of the cylinder heads which do need good airflow and the blades are, well there proper blades. I took this up with John Deakin and he appologised and agreed. I also questioned him on the tuft test he conducted on the inside of the engine nacelle of his Bonza which he videoed and verified that bum to wind runups resulted in improved flow through the engine. He had no answer why it occoured except that it did. I'll need a little more convincing before I start doing bum to the wind runups. It's like feeding a horse a carrot from the wrong end, it's just not natural, poor horsemanship to I suspect. Regards M |
Well I have looked at the first 10-15 odd cm of my propeller and I can't see anything particularly aerodynamic about it...I looked at a prop on a spitfire a few months ago at it is all 'blade' from the spinner out. I guess it varies widely as you suggest...but the fact remains that not much cooling airflow gets 'pushed' into the cowl by the prop in your average GA aircraft stationary on the ground.
But as with all things you invariably expose yourself when you attempt 'simple' explanations. I don't spend days or weeks researching my posts before hitting submit, they come from long experience. Capt WE Johns...no the DC3, Caribou and Harvard don't count with respect to the comparison I was making. A37573 was suggesting anyone irresponsible enough to do checks 'on the run' in a typical GA light single or twin should/would be hung, drawn and quartered, in the RAAF. They could be quite safely done in a CT4 but it is not RAAF SOP and neither is it GA SOP with ab initio students..and that is fine. I would never suggest anyone do checks on the run in a DC3, Bou or Harvard...and I've flown 2 of them....hint, not the Bou:ok: They are not Barons, Bonanzas, 210s, 310 or Chieftains....for starters the Dak and some models of Harvard have no tailwheel steering...just taxiing them is an art without attempting mag/prop checks concurrently. I guess it gets back to 'uncommon' common sense....and most of us aren't in the airforce.:ugh: |
Chimba
I appreciate the fact the cooling air is drawn in by deck pressure differential. And to on follow on that it is apparent that it is the outer extremities of the blade section that have the most influence on static cooling efficencies, as it is this section that is accelerating the air past the cooling air outlet. Now in a mild downwind I'm sure that the props airstream velocity has dominate influence on proceedings. But above a mild downwind component I wouldn't mind betting that the prop wash starts to suffer from the same principal problem that choppers trying to hover in ground effect have, vortex ring I think it's called. Any way you know all this and I think you probably explained it better back further. As a side note to others, and this probaly belongs in the ground leaning thread. Those who are trying to clear fouled plugs with a hard runup should realise that if the plug is carbon fouled you can usually burn it off and clear the problem. However if you have suffered lead fouling you cannot burn it off, you need to physicaly dislodge the small bead of lead that is shorting the electrode, this is where cycling a prop at higher RPM might I say might help. Other wise it's a trip back to the tool box. Lead fouling is most likely to occour when combustion temps and plug nose temps are low and the chemical lead scavenging agents in fuel won't work. Another good reason to keep ground mixture's lean and minimise time on the ground. Another rant M |
Someone asked a while back where a good place to do runups is when there is not one designated. I have also come accross this once or twice. The first time it led me to doing runups in a twin on the roll which took up a lot of effort on the taxi and I'm sure my instructors wouldnt have been happy. Bit dodgy of me.
Runups before each flight is -as I understand- in my ops manual and I would prefer to do it when not required by ops manuals cos things do get missed when you leave it to other people. I find into wind helps at GAAPS because it makes ur aircraft's position and entry/exit in the bay predictable to other aircraft and since the aircraft will all point the same way, you won't be prop washing others. Personally I have few problems with checks on the run, good practice for larger operators. I follow their procedures such as pausing checks when crossing runways and 'clear left/right' approaching taxiways. Of course all subject to workload, safety first and speed/efficiency second etc etc. |
Vh-ajm,
Good question, where to runup when none is provided. They way I and most seasoned pilots would mostly tackle this is to start up and quietly idle away some where discreet and into wind and where your prop wash won't annoy anyone. And with a clean surface under the props. A simple key to this is to consider this matter before you even get in the aircraft. As you might even want to wander over to a pre selected area and check the surface suitability for blue metal/gravel. Now if you don't have the luxury of a clean surface under the props, set your idle nice and low say 700-800 RPM consistant with smooth running and lean to max increase in RPM. When the RPM comes up a bit which it should, reset to that 700-800 RPM again. Be aware even with proper leaning some engines will still lead foul at these low RPM's due still not being hot enough to activate the lead scavenging agents. If your in an aircraft that is a bit inclined to foul on the ground then choose 900-1000 RPM Do all your checks bar the engine runup then taxi off, do the runup bit on the run and quickly ish, you need very little head in the cockpit for a mag check and prop cycle/feather check. Particularly with a bit of practise, if the taxi route is going to be along gravel do this brief runup while taxiing into wind if you can. Grass is often better to run up over than asphalt as it has a great ability to impeed the votices that occour under the prop in addition to also impeeding the movement of gravel/stones that lie within it. Your SOP's have the final word though. Regards M |
Thanks Mic,
Pretty much what I did last time. Was just a bit hairy doing it assy. Nice long taxiway though so it turned out ok. Have been told to do checks at the hold point before but figured the jet behind me wouldnt have been to happy about that. AM |
In the best interests of your propeller….
When operating on a gravel/loose surface always try to keep moving with minimum power - ESPECIALLY with a tailwind. Try to make all turns into wind - again using minimum power. Try to avoid stationary runups - ESPECIALLY with a tailwind. Try to maneuver your aircraft so that you will be starting into wind. A while ago I observed a light twin turn to line up through a tailwind on a gravel runway. The whole aircraft literally disappeared in a cloud of dust as the wind came through the rear quadrant. A little bit of situational awareness goes a LONG way with regard to prop care. IMO it is good airmanship to employ these techniques on any runway, sealed or un-sealed. You might get away without giving much thought to it, but it doesn’t look very professional and I wouldn’t want to be the poor bloke who has to pay for the prop overhauls! |
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