a real question here

[BoostedNihilist]

In a thread over in general someone mentioned taking off without full power (in a 172) in contravention to the POH/AFM

Now, I have a few questions actually.

If it is against the POH and you crash are you 'wrong' ?

If these 'rules' are written in blood is it okay to experiment with them if you see no harm in doing so?

finally my real question.

IF you are doing a less than full power takeoff is it possible to be stuck on the reverse side of the power curve and unable to makeup the airspeed to overcome the drag/friction etc to get on the positive side?

[mcrit]

From a legal stand point there is a CAR that says you will operate an a/c according to approved documentation (POH, Company SOPs etc). So, if you were to crash doing a reduced power take off in a 172 you could find yourself in a bit of hot water.

As for experimenting......tough call. Depends on your experience and how much you want to experiment. I'd seek some advice before you started.

Depending on the power/weight/density altitude you could get stuck behind the power curve (ie hit a lock point). I think the 172 would have enough power to pull you back to the front side of the power curve, but I wouldn't want to verify that via experimentation.

[iflyforpie]

I believe there was a Navajo crash a while ago where the use of reduced power settings was a factor in the crash and was not approved in the POH/AFM.


As far as being stuck on the back side of the power curve it is a very real scenario at my airport for normal 172 operations. If you are fully loaded on a hot day and are trying to pull the nose up to clear the obstacles you are going to have some problems.

My experience with the 172 (M model 150HP) is that using no flaps and best angle is bad while using 10 flaps and best rate is best for clearing obstacles.

[Ralliart]

iflyforpie,

In your post, you start off by mentioning a Navajo crash that was attributed to non-standard AFM procedures.

Then you go on to say that in your experience you prefer to use a certain climb technique because you think it's best for clearing obstacles.

Do you see the irony?



The 172M POH states for max performance takeoff:

1) Wing Flaps -- Up
2) Carburetor Heat -- Cold
3) Brakes -- Apply
4) Throttle -- Full
5) Brakes -- Release
6) Airplane Attitude -- Slightly tail low
7) Climb Speed -- 68 MPH (until all obstacles are cleared).

Quote: using no flaps and best angle is bad


In another thread, you commented:

We don't have a full load checkout here, but taking off in a 172 max gross on a hot day with no wind can be scary at my field.

If you think something is scary, why would you attempt it in the first place?



I'm not trying to pick on you or single you out, rather I'm just mentioning a couple observations that seemed odd to me.

[basher]

Deleted

[fougapilot]

Reduced power takeoff are a reality, but not in small GA airplanes.

They exist on larger jet (ie Airliners or large corporate jets) to extend engine life.

The logic is as follows;

When operating from a long runway, use a reduced engine thrust for the airplane to use nearly all the available runway.
For example, a jumbo might need 5000ft of runway to takeoff under a specific weight/altitude/temperature (aka WAT) using full power, but the airplane is operating from a 12 000ft runway. So, the crew looks into the AFM (probably the FMS, but the chart exist in the AFM) for the reduced thrust takeoff chart and determines the required thrust for operation on a 12 000ft runway and the same WAT. Thus using less power to accomplish the same task; getting the bird off the ground. And "taxing" the engines less which increases engine life and airline profit.

So, the airplane will simply take a longer time to accelerate and get off the ground, but that is not a big deal, it has more than twice the runway length required under normal circumstances.

Now, this being said, should there be an emergency the crew can and will use all available power.

These reduce power takeoff procedures are listed in the airplane AFM and approved by the FAA/TC and the likes. They are 100% safe and legal.

However, unless there is a specific reduce power takeoff chart in your AFM/POH, the takeoff power stated usually is a MINIMUM takeoff power required to meet the performances of the takeoff / obstacle clearence charts.

F

[KAG]

I believe your talking about big pistons forever, and his reference to using reduced power as a teaching aid. Is it legal - no, it goes against the POH.
BUT, it's a realistic example of what the plane would behave like on a high DA field or with a full load. These planes develope full power at standart ICAO day, which few places and times are exact.

Is it smart to do? With the experience Big pistons has yes. As a newbie no, don't try it.

Sometimes what is "legal" and "smart" are two different things. It wasn't legal for me to take my PPL students IMC when doing instrument time but I did it to prove a point - stay the hell out of cloud until you have an IFR ticket. So I can see him using this as a teaching tool, but do not confuse it with a normal procedure.

As a side note...
If (when) anyone finds themselves taking off and the plane just isn't preforming (mushing along near ground effect) lower your nose and point it at the trees!!! get your speed up then pull up to clear them. "I'd rather see you clear the trees by 10' and 100 KTS rather then 100' and 60 KTS" - quote from a float driver, saved my ass a time or two.

[iflyforpie]

iflyforpie,

In your post, you start off by mentioning a Navajo crash that was attributed to non-standard AFM procedures.

Then you go on to say that in your experience you prefer to use a certain climb technique because you think it's best for clearing obstacles.

Do you see the irony?



The 172M POH states for max performance takeoff:

1) Wing Flaps -- Up
2) Carburetor Heat -- Cold
3) Brakes -- Apply
4) Throttle -- Full
5) Brakes -- Release
6) Airplane Attitude -- Slightly tail low
7) Climb Speed -- 68 MPH (until all obstacles are cleared).

Quote: using no flaps and best angle is bad


In another thread, you commented:

We don't have a full load checkout here, but taking off in a 172 max gross on a hot day with no wind can be scary at my field.

If you think something is scary, why would you attempt it in the first place?



I'm not trying to pick on you or single you out, rather I'm just mentioning a couple observations that seemed odd to me.

No problem. But I will try to justify these statements.

First, climbing at faster speeds than recommended is far different than climbing at slower speeds than recommended. Engine cooling is better, you are on the front side of the power curve, and a simply tug on the stick will allow your aircraft to zoom up and reduce speed if you find you aren't getting the performance that you want. After all, how many of us do cruise climbs?

I am very aware of what the 172 POH says and remember hashing out the whole obstacle vs no obstacle method in a heated debate during a ground school I was teaching. However this was when my experience was taking off on a 6000 foot runway at about 4000 DA.


If you follow the POH in my 172, taking off from my current airfield at max gross where DA sits around 5-6000 feet and there are obstacles at both ends, you will mush along in ground effect until the plane finally gets over the 'hump' to the front side of the power curve and begins to sluggishly climb. It will do it, but if you get a panicky pilot who keeps pulling back on the stick, bad things will happen. It will not climb beyond ground effect at the recommended obstacle clearance speed of 59KIAS.

However, if you put out 10 degrees of flap, accelerate to 70 knots by keeping the nose down and then climb, it becomes a totally different aircraft easily clearing the obstacles. I demonstrate both methods to renters and let them see the difference for themselves.





As far as something being scary. A spin is scary to most people, but perfectly safe when done in the correct aircraft in the correct manner by someone who has been trained.



And as far as following the POH I try to fly every plane by the book, but I am not going to be so hell bent to follow the book as to fly the plane into the trees. Reducing the engine power introduces more risks IMHO than climbing at a faster speed.




PS KAG. You are right on!

[E-Flyer]

In a thread over in general someone mentioned taking off without full power (in a 172) in contravention to the POH/AFM

Now, I have a few questions actually.

If it is against the POH and you crash are you 'wrong' ?

If these 'rules' are written in blood is it okay to experiment with them if you see no harm in doing so?

finally my real question.

IF you are doing a less than full power takeoff is it possible to be stuck on the reverse side of the power curve and unable to makeup the airspeed to overcome the drag/friction etc to get on the positive side?

Here's a good rule that i always stick my butt to.
Do what you're supposed to do, you won't be messing with reduced take off power settings, D-TO, FLX or any of that kind of crap until you hit the more powerful, higher performance based aircrafts.

Honestly, this question should be posed to your AME or an AME... they would have a good answer for you as of why or why not that would be a thing to do.

[square]

IF you are doing a less than full power takeoff is it possible to be stuck on the reverse side of the power curve and unable to makeup the airspeed to overcome the drag/friction etc to get on the positive side?

Slow flight is no mystery, you're in it when you're slow, period. At full power, below Vy is the backside of the power curve. The top of the power curve is the optimal angle of attack, so at a slower speed the top of the power curve would be slower too. I.. think.

[iflyforpie]

The top of the power curve remains the same for a given power setting. Vy is the top. Vx is just behind it. For power off best glide is just in front of the top of the power curve and best endurance glide is on the top.

[BoostedNihilist]

If my instructor suggested this I would get out of the plane and walk to another ftu...

and then phone transport.

This suggestion is illegal and rediculous when there are other perfectly acceptable solutions within the limitations of the POH.

[square]

If my instructor suggested this I would get out of the plane and walk to another ftu...

and then phone transport.

This suggestion is illegal and rediculous when there are other perfectly acceptable solutions within the limitations of the POH.

Huh? What suggestion?

[BoostedNihilist]

seriously?

his reference to using reduced power as a teaching aid. Is it legal - no, it goes against the POH

.


Essentially this means if you are trying this method, and something goes wrong, or you @#$! it up, (and hopefully you don't kill anyone) people will call you an idiot... because you would be being one.

beyond flying, to knowingly disregard a safety rule simply to demonstrate a concept is completely unprofessional and imo the height of stupidity not to mention selfish. That type of conduct is unacceptable in all but the most dire of emergencies when potential risk can be
justified.

Sometimes what is "legal" and "smart" are two different things. It wasn't legal for me to take my PPL students IMC when doing instrument time but I did it to prove a point - stay the hell out of cloud until you have an IFR ticket. So I can see him using this as a teaching tool, but do not confuse it with a normal procedure.

Hmm, what happens if the student has no problems in the cloud? logically wouldn't that boost his (false) confidence? You won't be there with him every time, and if he needs you to baby him through a fairly obvious and clear decision perhaps you should reevaluate your teaching methods or student selection.

Also, if he is a tecaher, and he teaches daily, would it not then be a normal procedure. Sounds like a chronic disregard for safety and aviation law to me.

Personally, I think every ppl should have that experience but your motivation is seriously questionable. It should be to gather data for yourself, to evaluate your skill as an instrument instructor, not to teach a rudimentary decision making process... seriously.

I reiterate this thread is about 172's

[StudentPilot]

Let's say you're a flight instructor with a student with 45 hours that has passed all their exams. Due to an addition error or whatever reason, you need to do one more flight for them to meet the dual requirements for a PPL. This student doesn't quite understand how much of an effect high density altitudes effects the airplane, despite numerous attempts to teach them - and most apparent when they got questions about it wrong on the written/flight tests. Their training is all done near sea level (no higher elevation airports nearby) and near standard temperature. As you walk out to the 172 you are chatting, and they mention they are taking a private 172 down to Colorado the following week. They plan to fly to Leadville, elevation 9927', in the middle of the summer with a full load.

What do you do?
-Refuse to fly with them so they cannot get their license (with you at least) before the trip unless they go to another FTU/instructor
-Try to teach them about DALT on the ground again
-Reduced power take off to simulate being hot, high, and heavy on a long runway, with additional power available, so they can see the effects themselves
-Do nothing or suggest they not go there and hope they don't crash and/or die
-Something else

[BoostedNihilist]

What do you do?
-Refuse to fly with them so they cannot get their license (with you at least) before the trip unless they go to another FTU/instructor
-Try to teach them about DALT on the ground again
-Reduced power take off to simulate being hot, high, and heavy on a long runway, with additional power available, so they can see the effects themselves
-Do nothing or suggest they not go there and hope they don't crash and/or die
-Something else

This is seriously scary.

How could we possibly replicate heavy?

These conditions are like sex, you get a feel through experience. Your initial training should be enough to get you comfortable in those situations and if you didn't get great instruction or you don't feel safe then don't fly.. if you don't know how to make those decisions then you shouldn't be flying. People have to know their own shit for themselves. If they don't know their own shit, then it is your fault as a teacher, and as a student.


Not to mention, you're going to let a guy, fresh out of a ppl take a plane and fly from sea level to colorado.. give me a fucking break!

[KAG]

seriously?

his reference to using reduced power as a teaching aid. Is it legal - no, it goes against the POH

.


Essentially this means if you are trying this method, and something goes wrong, or you @#$! it up, (and hopefully you don't kill anyone) people will call you an idiot... because you would be being one.

beyond flying, to knowingly disregard a safety rule simply to demonstrate a concept is completely unprofessional and imo the height of stupidity not to mention selfish. That type of conduct is unacceptable in all but the most dire of emergencies when potential risk can be
justified.

Sometimes what is "legal" and "smart" are two different things. It wasn't legal for me to take my PPL students IMC when doing instrument time but I did it to prove a point - stay the hell out of cloud until you have an IFR ticket. So I can see him using this as a teaching tool, but do not confuse it with a normal procedure.

Hmm, what happens if the student has no problems in the cloud? logically wouldn't that boost his (false) confidence? You won't be there with him every time, and if he needs you to baby him through a fairly obvious and clear decision perhaps you should reevaluate your teaching methods or student selection.

Also, if he is a tecaher, and he teaches daily, would it not then be a normal procedure. Sounds like a chronic disregard for safety and aviation law to me.

Personally, I think every ppl should have that experience but your motivation is seriously questionable. It should be to gather data for yourself, to evaluate your skill as an instrument instructor, not to teach a rudimentary decision making process... seriously.

I reiterate this thread is about 172's

Personally I never taught reduced power takeoffs. I didn't have the experience I have now, or even the knowledge that they even were done operationally, and I probably wouldn’t do them myself even now.
That being said, the first time you do a high DA, max gross takeoff as a newly minted pilot your probably going to wish you had at least seen it, or had some idea what it was going to feel like prior to shitting your pants with your friends on board.

But I stand by my taking every student IMC as an IFR rated instructor. Yes it goes against the law, then again, students will try stupid things, and unknowingly or ignorantly place themselves in harms way. I “motivated” them not to try it.
And since not a single student was able to keep the plane right side up, nor have any of them been killed in the decade since I taught them, I say the demonstration worked.

Stupidity, Lack of professionalism? I think not. I think allowing newly minted PPL/CPL pilots in night IMC in a black hole environment is stupid and unprofessional, then again it’s legal.

[atpl53]

Wow...!!! Scary stuff. The law of "PRIMACY" prevails. Take a student into IMC to demonstrate why not to go into cloud is ...well, ridiculous...I taught for four years and never resorted to such stupidity. Funny, my students all got the concept by the traditional approved teaching methodology. But...I'm certain that you filed an IFR flight plan, right. Whew!!!...I'm just waiting as an IFR rated pilot on an IMC day to see you in cloud....NOT!!!

[KAG]

Wow...!!! Scary stuff. The law of "PRIMACY" prevails. Take a student into IMC to demonstrate why not to go into cloud is ...well, ridiculous...I taught for four years and never resorted to such stupidity. Funny, my students all got the concept by the traditional approved teaching methodology. But...I'm certain that you filed an IFR flight plan, right. Whew!!!...I'm just waiting as an IFR rated pilot on an IMC day to see you in cloud....NOT!!!

Primacy, wow, there’s a word I have totally forgotten its definition.

How is it ridiculous when you sit down with a student, show them the 178 seconds handout, and see the doubt cross their face? Every student I asked after a few hours of hood time all thought they could fly into and out of a cloud safely. I even showed them a clip of a friend of mine who was killed in a black hole go around, and explained the similarities between black hole flying and IMC flying. Explained about the human factors relating to your ears, and the acceleration and turn errors. They still didn’t fully believe or understand. They did after that exercise!!!
I can’t tell you how many new hires I trained on King Airs with IFR tickets that had never been IMC before, and trust me it showed. That is ridiculous!!!

And your right I was on a VFR flight iten, not that it would have made any difference in a non radar, uncontrolled chunk of airspace, and as long as you were listening on 126.7 and doing proper position reports, then it wouldn't have been a problem.
Didn't say it was legal, but it was a great learning tool.

[StudentPilot]

It definitely isn't a likely scenario, but it is possible.
An instructor has no control what a licenced PPL does with a private aircraft - if they want to fly from sea level to 10 000'+ DALT, they can. As for learning through experience, I fully agree everyone should know their own limitations, but what if the student feels they are safe to do the flight and know what they are doing? I know I wasn't subjected to any tests to see if I had a reasonable knowledge of what my limits were. Also, is it the instructor's fault that the student doesn't know absolutely everything? What's the passing grade for TC's exams? Unless it's bumped up to 100% very few (ie zero) new pilots will know everything, and gaps in their knowledge should be expected when they get licenced. As for replicating being heavy, throw a bunch of heavy items sitting around the hangar in the plane, get a couple people that aren't doing anything to go for the flight, or use reduced power if you're planning on doing it anyway.

I did do one or two reduced power take offs during my training to simulate hot days with a full load, so maybe I'm biased since I enjoyed actually seeing (well, a close approximation of) the difference. Unfortunately there weren't any big hills around to learn in actual hot & high conditions.

[Strega]

The top of the power curve remains the same for a given power setting. Vy is the top. Vx is just behind it. For power off best glide is just in front of the top of the power curve and best endurance glide is on the top.

can you justify this?

[TC Aviator]

Guys, there appears to be some confusion between "recommendations" and "limitations".

602.07 No person shall operate an aircraft unless it is operated in accordance with the operating limitations
(a) set out in the aircraft flight manual, where an aircraft flight manual is required by the applicable standards of airworthiness;
(b) set out in a document other than the aircraft flight manual, where use of that document is authorized pursuant to Part VII;
(c) indicated by markings or placards required pursuant to section 605.05; or
(d) prescribed by the competent authority of the state of registry of the aircraft.

The manufacturer spent millions to determine the operating envelope and establish the limitations that are published in the Limitations Section of the POH/AFM. The balance of the POH/AFM consists of the minimum "best practices" applicable to most situations. A pilot may vary from the recommendations, but must always apply good airmanship to remain within the engine and airframe limitations and ensure the safety of the flight.

I would recommend full-throttle (max power) takeoffs and initial climbs in lighter aircraft until gaining a safe height AGL. Reduced-power takeoffs are not illegal, failure to maintain safe flight is illegal.

[xsbank]

The problem with changing the 'rules' to 'simulate' a situation, like a reduced-power take-off to simulate a full load or a high-altitude takeoff, is that you are just guessing at the simulation. What is the power setting that simulates a hot day? What is the power setting that simulates high altitude operations? Are you able to meet the performance levels that are written in the charts?

The answer is that you just don't know and you are just making it up as you go along, placing your student in a perilous situation. Do you expect the student to practice low-level power take-offs by himself? Fly in cloud, breaking a lot of rules, to practise 'instrument' flying?

Showing someone that you are routinely flying in cloud or using low-power take-offs, against the rules or against good airmanship has definitely taught him a lesson - its alright to break the rules or practice poor airmanship if he thinks there is a reason for it. Is that your purpose in "showing" them this nonsense, to pass on the worst habits that you have developed in your teaching career? What exactly are you trying to teach them? That to a 'superior pilot' the rules have no meaning?

You cannot teach a student everything in one setting, you need them to mature and develop their own level of knowledge. One of the ways you can do this is to encourage them to stay safe - showing them that its ok to break the rules or practise poor airmanship is not one of them.

Perhaps you should read my other article on Darwinism.

[Big Pistons Forever]

The arguments in this thread appear to have polarized into two hard over positions, with a significant number of posters holding the strong belief that using a reduced power takeoff as a teaching metheod is not something they would do under any circumstances. Fair enough always using full throttle is a safe and prudent way to operate an aircraft, although as I have said earlier I am personally comfortable, and have had good success , using this the reduced power technique as a teaching aid. But it got me thinking about how I would advise a flight instructor who wanted to make sure the student had a practical appreciation of the hot and high scenario but was not comfortable using reduced power.

One way would be to as part of some other exercise climb to about 6000 ft density altitude set up level flight at Yy and then go to full power and climb for three minutes and note how much altitude you have gained. After you get on the ground go find a nice high airport (preferably with some hills nearby) and measure the distance traveled in those three minutes on the chart and then compare the terrain elevation with the alttutude gained. After just experiencing the anemic climb performance you can paint a vivid verbal picture of how easy it is to get into trouble in even an area of very slight rising ground.

The bottom line from my POV is I feel strongly it is the responsibilty of the instructor to adequately prepare their student. The TC sylabus is the minimum standard, instructors should IMO aspire to a higher standard. With a little imagination you can enrich the exercises with out taking a lot of extra time or costing he student much money.

[mcrit]

Nothing wrong with taking a PPL student into IMC (provided the instructor is instrument rated and you are clear of controlled airspace). It is certainly in line with the learning factor of intensity. ("So Mr. Bloggins.....how would you like to be in this situation all by yourself?") You aren't showing the student any bad habits, but you do have to be clear about the objective of the flight ("I'm not showing you this so that you can do it on your own, I'm showing it to you so that : 1) you see how easy tricky it is and 2) should you ever inadvertently get yourself in a mess like this it won't be completely foreign to you")