Full flaps
- Thread starter Dazzler
- Start date
So what changed? I was mearly slinging it back. As for the understanding of what you guys are talking about, I haven't been able to get it to work, and two people say they have. I have tried and tried at my own expense, so mabey you should slow your role as well. It's not like I am trying to not justify your actions. I fly in So Cals airspace, where an engine failure on final is deadly. I also come from a long line of pilots who do nothing but preach about makeing sure you have enough energy to make the runway when the engine quits, as they have all lost friends in single engine airplanes because the engine quit on final. Flying is all about risk management. I also come from somewhat of the old school, and have almost equal time in airplanes that don't even have flaps as ones that do. So IMHO, light airplanes don't even need flaps. Do I let my students carry power on an approach, you betcha. Do I let them keep the power on when there high, no effin way, power to idle, flaps to control airspeed in descent. I tend to think of them as "drag buckets." And as a general rule, here's how I teach the pattern.
"Down wind abeam, carb heat and 15, flaps 10 inside the white arc, pitch for 85, begin your descent. Rolling out on base, pitch for 75. Turning final, pick your aiming point, reduce power if needed, flaps 20/30 to increase your descent angle (40 if you got 'em) if needed, and keep it at 65." Now, with the way thats tought, if the engine should quit, you will have to do nothing but continue to fly the airplane, no re-configuring needed. It takes a few variables out of the loop. What is so wrong with that?
My understanding of aerodynamics works just fine. The questions I ask are based on the FAA books, and what is written in them. That is what I am supposed to teach to. Not some other terms, however correct or incorrect they might be. If my student pulls out some "Aerodynamics for dummies" book during a checkride, you think the examiner will like that much? Disclaimer--- I am not calling anyone involved in this thread a dummy. Oh yeah, one last parting note. I've never busted a ride, and I have never had a student of mine bust a ride either. I think my understanding of aerodynamics, and teaching habbits are just fine.
tgrayson
New Member
This is where terminology becomes a problem.
AoA, as normally used in the aerodynamic literature, is with reference to the chordline of the airfoil without flaps, even when flaps are deflected. So, by definition, flaps do not change AoA merely by cause of their deflection.
This is why at a constant airspeed, an airplane with flaps lowered flies at a lower AoA than one without flaps. If you define the chordline differently, such as using the line from the leading edge to the trailing edge of the deflected flap, that may useful in explaining how flaps work (kinda, sorta), but that definition is non-standard and will cause comprehension problems when reading more conventional explanations of airfoils. When learning about any subject, it's best to learn to use its terminology if you hope to make any progress.
As for approach speeds in 172s, I use 65 knots/70 MPH.
O.K. tgray, then we are on the same page now. Walk me through how you do this one more time, step by step if you don't mind (I know it will probably involve a bunch of typing, sorry) so I can try this one more time, and see if I can get it to work. And one more quick question, if you are, say, 1/4 mile from the runway, are you still going to retract the flaps? I think I am begning to wrap my head around this. I would do it on a long final, say 2-3 miles, but I still don't think I'd slam 'em up when 1/4 mile from the runway.
tgrayson
New Member
If I were you, I'd certainly experiment with some altitude below. Once you get comfortable, you'll find it's no big deal at lower altitudes.
BTW, the first time that this concept was shown to me was by my original instructor, who flipped the Cessna flap switch up while floating down the runway. He just gradually raised the nose in concert with the flaps raising, so that we remained at essentially the same distance above the runway. He claimed to get exceptional short field results using this technique, something I'm a bit skeptical of.
The second person who did the same thing with me was William K. Kershner, who demonstrated a speed of heat approach in a C152, with fishtailing on short final to lose airspeed followed by raising the flaps in ground effect and a resulting turnoff at the first taxiway. (Hmmm, maybe there's some truth to the short-field application after all.)
I demonstrated this to a student a while back. I failed the engine on a C172M on final, with 40 degree flaps. Once it became clear to him we weren't going to make the runway, I had him raise the flaps. I had instructed him just to keep raising the nose as the flaps came out, but he chose instead just to keep increasing the AoA to prevent the airspeed from rising. It worked just as well. Not only did we make the runway, but we floated halfway down it before touching down.
You don't have to get it perfect for it to still be of immense help. You mainly want to prevent that big sink you normally get with flap retraction. If you overdo it or underdo it a bit, no big deal, just fix it as the airspeed deviates from best glide. If you feel your stomach rise the way it does in a descending elevator, you haven't pulled enough.
BTW, years ago, I failed the engine on a guy who had strayed too far out on base. He'd already put in 20 degree flaps in. We had not done any of the training that I describe here, but I saw him looking at the flap lever as it became clear we'd never make the runway. As he looked back and forth from the lever to the runway, I was thinking "Is he going to do it?" Finally, he reached over and slapped the flap lever up. We sank of course, because he didn't increase his AoA to compensate, but even so, our glide flattened out as he kept the magic 60 knots and we actually ended up touching down inches past the runway threshold. The point being that even poorly performed, getting the flaps out is almost always a good idea, unless very close to the ground.
I'm working on the video idea, but it'll probably take a couple of weeks to put together.
So from that post, you do it when your a long way out from the runway, and just use pitch to maintain best glide (thats the way I read it)?
tgrayson
New Member
I'd pitch to eliminate the sink. Having an idea of the difference in AoA between the flapped and non-flapped configurations gives you a ballpark. If you eliminate the sink, you know you've established the correct AoA and the proper airspeed will materialize. And no, I wouldn't restrict this to just far from the runway....that's only for practice. It works at any point in the approach as long as you have a suitable airspeed for a non-flapped approach, or have enough altitude to achieve that speed.
The problem I have been having is that when I pitch to eliminate sink, I loose too much airspeed, and get below best glide. What am I doing wrong? I'll describe to the best I can what I have been trying.
I pull power to idle, to simulate the engine failure, I give it about 2-3 seconds (what it usually take to realize an engine failure), and then I bring the flap lever to 0 deg. As the flaps come up, I use my stomach to tell if I am sinking (VSI's ride the short bus, so I try not to rely on it when seconds count). Everytime I do, I find my runway moveing up in the windscreen. If you say it works, than I am doing something wrong.
tgrayson
New Member
I guess I'm a little confused. If you lose too much airspeed, that suggests pulling back too aggressively. If you have the runway moving up in the windscreen, that suggest not pulling back aggressively enough...the runway ought to be moving down in the windscreen as the nose comes up. Are you sure you aren't losing the airspeed in the 2-3 seconds delay?
BTW, even if you pull up too aggressively, it's not that big a deal; you've stored some of the energy of the airplane in extra altitude that you can use to resume your best glide speed.
SpiraMirabilis
Possible Subversive
This IS a tried and true method and has worked since the invention of modern flaps. Sorry... I take offense when you say that tgrayson is teaching his students "how to kill themselves."
Next time you go up with a student, if you are willing, on the flight back ask for the plane for a minute. Brief your student as to what you are doing just so they aren't scared, you know the drill. Now idle the engine and add flaps while slowing up and getting a stable best glide trimmed descent. Once stable, hands off, put up the flaps and gently pull back looking outside using your stomach like you did but having your student callout the changes in airspeed/VSI so you can at least see it happen and get a feel for it. Then take it to the pattern and try it there once you know how to do it at altitude.
You are basically a first time student trying to do turns around a point and entering the maneuver by diving to altitude over the point. Then while in the maneuver you are trying to set up something you have never done before while looking for something you didn't think existed a week ago. I mean absolutely no disrespect, I am merely saying you might have a better result if you stabilize the aircraft first.
I have done this many times in my training and for my tests a few days ago I did the stable at altitude approach so I could easily see and verify the results. One note on that experiment, you will raise the nose to stop the sink then slowly lower it to a normal best glide descent as the speed rebuilds. You will loose about 5 knots which is ok, that is actually min sink speed and will keep you airborne for the longest time, and then regain this 5 knots when lowering the nose.
PS...Safety...Maslow's Hierarchy of Needs...
Some students don't need to be taught how to kill themselves.......
Some are professionals with experience...
http://www.brantfordexpositor.ca/ArticleDisplay.aspx?e=1527507
This is why I am also so confused. I am pitching to maintain airspeed, and I can keep it almost deadlocked at 65kts (+/- 1kt), and I am sinking like mad (more than 100ft), hence why I think I am doing something wrong...
Get me a video man. Just mount it somewhere that I can see th e big picture (6pack, flight controls/pilot, out the windscreen). Mabey put it right between the seats, about shoulder level, pointed slightly off to the left (only slightly). Almost as if Jim Bob was in the back seat filming his buddy.
If it's so tried and true, then why is everyone I have talked to about this completely disagree with it (not just "rookie" cfi's, but men who are Master CFI's((one of them a Master Aerobatic)), Gold Seal CFI's, and one in particular, whos has 15k dual given, and is weeks away from attending DPE school in Oaklahoma).
If it offends you what I say, then turn of your computer. Your not obligated to read what I have to say. There like a-holes. We all got 'em, and they all stink.
ppragman
FLIPY FLAPS!
A poweroff gliding approach will not give you enough fine tuned control to prevent high sink rates in larger piston singles, nor will it allow to fly as slow and land as short in the same type of aircraft without perfect timing and a shot of power in the flare, nor will it allow you to adequately set up (imo) for a soft field touchdown when its really soft.
Look, the point of the traffic pattern isn't to keep you within gliding distance at all times, frankly, that's impossible, the point of the traffic pattern is to have a standardized way to sequence aircraft into and out of the airport. ATC won't even allow you to fly a "short approach" on every touchdown. Further, what are you going to do when you get slowed up and they have you "extend your downwind tower will call your base?" Fly really high when you're outside of gliding distance of the airport so as not to be, then drop down to pattern altitude exactly when you have gliding distance and then pull the power and glide in? Nahhhh, I'll pass.
Further, if you lose a motor on final, theres a good chance that any wind you have (whether you're power on or power off) will change, and you won't be able to make the airport anyway. All you can do is lower the nose, and land straight ahead in cessna products (because the flaps don't retract fast enough imo) and dump the flaps then milk them in in the flare (because that johnson bar is insantaneous) in piper products. Look, an airplane spends most of its time away from the airport out flying (other than a training plane) there's a good chance that on many of your flights you don't have any suitable runways to glide to, or what looks like an adequate place to land is in fact inadequate and you won't be able to know until you're in the flare because whatever is dangerous is obscured from above. Frankly, unless you're flying over Kansas/Iowa/Insert Agricultural State/etc you're probably not going to have too many places to land on a given flight, and then that being said, if you spend all your time worrying about that, and don't concentrate on the factors which are more likely to kill you (which is pilot error usually, or bad technique, or weather) you'll overlook some of the more important things about the flight.
At this point, I'm rambling, but again, I bring up the point: flying is risk management and situational control. Failing to adequately manage risk (in this case being too concerned with the final few seconds of a flight) would probably result in some situations you would be unable adequately control the aircraft on short final. Ask yourself, how do commercial operators fly the fleets of Caravans hauling pax out there? Do they chop&drop approaches? No. They fly a fairly stabilized (I use the term loosely because there are no absolutes and sometimes its better to bomb it over) power on approaches because on average, they are safer, and offer the pilot a larger margin of error for conditions outside of the ordinary.
You are 100% correct. And when the engine does quit, I would rather flip over on the runway (at 35kts), becuase I didn't have any power to add, than not make it at all(in a stall 100ft up).
It is possible, on a normal pattern (from most points). But when you get extended, and the engine quits, you are kinda eff'ed, and I had never mentioned this because most airports do this less than 1/3 of the time(most, not all), and the bottom line is you can't prepare for every scenario in every situation. I am not advocating the things mentioned in this paragraph (i.e. flying a high pattern). But I would like to prepare my student to make it back to the runway from anywhere that altitude permits. Otherwise, find somewhere else to put it down. Remember the thread was started off of when to add flaps, not how to perform a power off appraoch, and all I am saying is wait to add flaps till as long as possible to mitigate the use of power to reach the runway.
I hear your point, and a caravan is much less suceptible to engine failure than a piston engine, hence, the higher TBO's. And when you have pax in the airplane, a chop and drop is not always the proper option. But I don't usually teach commercial pilots, I teach mom and pop who want to go out for sunday fun. We are not talking about comercial pilots either, or else the thread may have been titled "When do you teach your students to add flaps on power off 180's" to which I'd still say them same thing, either use them to control your descent, or use them in ground effect to make you desired touchdown point. Rambling, yes. But I have noticed that about you
.I titally agree flying is risk management, and the pattern is where the risk is very high, becuase you have very few options and time when things get quite. So why not try and teach to keep the risk to a minimum.
ppragman
FLIPY FLAPS!
Rather Flip over? If you're going into and out of mush fields all day, I'd rather not flip over frankly. Slow flat approaches let you ease the mains on better, especially when it's both soft and short.
That sounds good and all, but when you've only got one shot to get in, I'd stronly recommend flying a more stabilized approach if you're going into a short strip.
Basically, what I'm saying is if you have a tool use it to make sure that you can get in safely, and properly the first time without difficult to control high sink rates and unstabilzed bombing runs.
Then We agree. When Necessary, yes, carry the power and realize that when she goes quite, your kinda screwed during max performance stiff like short and soft. BUt When you have the option, I'd rather be power off (especially in a flight schools airplane ((who knows what the last guy did during his flight))).
Don't forget, the "tool" (engine) is broken in this situation we have been discusing. But I do agree, a max performance (short or soft) landing will require some power management to some degree.