In flight power check procedures

[Chewie]

Hey all I've got a question regarding power checks for confined landings/off airport landings. All through my flight training I've only done OGE hover checks for confined areas, but i have heard my instructors and other pilots refer to performing power checks in the downwind(?) for a confined area. Can someone explain this procedure to me? I'm working on my CFI binder and would like to include it if possible, more of a real world application that I think my students would benefit from learning in addition to the OGE hover method.

 

Thanks in advance!

[Hovergirl]

The power check on the downwind involves making sure that you are cruising, straight and level (ideally with the carb heat off for this check) at a power setting that is lower than your max takeoff power, ideally 4-5 inches less (in a 22 at least - I've heard different rules of thumb for this, would love to hear what power differential others are comfortable with). You will need that extra power to slow your descent and hover (having lost ETL) at your spot, or to turn your descent into a climb when the unexpected wires/coyote/sudden wind shift pops up and you go around or lose ETL at a higher altitude (OGE).

 

(also, remember that your spot is at a lower altitude than you are cruising at, so you will have a little more power, but since I generally do my recon at 500 feet above the spot that difference is 0.5 inches -- not a big factor.)

[Mikemv]

Dear HoverGirl, please help me understand this power check. Keep in mind that I am in an EC120 or B407 for the last 13 years or so but was the first R22 Factory CFI in Florida in 1982.

 

Are you saying that if your downwind cruise power setting(MP) is 4 -5 inches less than max MP allowable as per cyclic chart for Alt/Temp then you should have sufficient power to land at LZ into wind or no wind 500' below?

 

Seems somewhat reasonable to me. Question is what is "Cruise" definition and is it standardized parameters prior to power check?

 

Thanks, MikeMV

Edited October 16, 2009 by Mikemv

[kodoz]

I had heard of but don't remember the specifics of Hovergirl's method (and am looking forward to feedback on it). I learned to do a power check during the high recon using the performance charts (estimated elevation of the LZ, OAT, and estimated weight). During my pre-flight I also figure the weight after 20 minutes of flight time so that mental math isn't necessary. What's appealing about Hovergirl's method is that it is based on actual performance rather than some back of the hand in-flight estimate, but the key thing to making it work is knowing what your power margin has to be to successfully land.

 

[edit]I knew this topic had been covered before, but it's just so far back in the archives that it's hard to find. Here are some links back if you're interested in seeing them [link], [link], [link], (gets good around the 18th post). If only there was a way to capture all this great info rather than rehashing it anew each time....

[Chewie]

The method she described is the one I'm talking about, nice to hear it spelled out lol! Like I said I had heard the basic premise of it but didn't really know the particulars!

 

So generally, you would want to maintain alt/airspeed in the downwind (does it have to be done in the downwind or just any cruising flight?) with 5 in/MAP less than MAP limit and you would have the power available to safely land and takeoff from whatever spot (confined/pinnacle/etc...) you're checking? Just want to clarify. Should also probably mention that I fly 300c's.

 

Also how would that transition from a piston to a turbine, i.e. MAP to Torque(?). Do they have a torque limit like pistons have a MAP limit? My experience with turbines ends at seeing and caressing them .

 

Not trying to pile all my questions on you HG, you just answered first!!

 

Thanks in advance again!

[r22butters]

Chewie Posted Today, 16:05

Also how would that transition from a piston to a turbine, i.e. MAP to Torque(?). Do they have a torque limit like pistons have a MAP limit? My experience with turbines ends at seeing and caressing them .

 

They do have a 5min. takeoff, as well as a max continous limit, for torque. They also have those limits for temperature, via the TOT (turbine outlet temp.)guage. And sometimes you'll reach the TOT limit before the torque.

[Goldy]

Dear HoverGirl, please help me understand this power check. Keep in mind that I am in an EC120 or B407 for the last 13 years or so but was the first R22 Factory CFI in Florida in 1982.

 

Are you saying that if your downwind cruise power setting(MP) is 4 -5 inches less than max MP allowable as per cyclic chart for Alt/Temp then you should have sufficient power to land at LZ into wind or no wind 500' below?

 

Seems somewhat reasonable to me. Question is what is "Cruise" definition and is it standardized parameters prior to power check?

 

Thanks, MikeMV

 

The one important thing missing is these comments is AIRSPEED! I learned the downwind power check in a similar fashion, but slow to 6o knots first. So, at 60 knots, if you are flying along at 3-4 inches under your max available power, then you should be ok, able to stop your descent, hover and land.

 

However, I still think the most important thing (where possible) is to keep in ETL until you are down low and able to get into ground effect. As we all know, being OUT of ETL, and OUT of ground effect, at a high DA, can end badly.

 

I was reminded of this on my approach to 6250' a few weeks ago. What fun in a Raven 1..

 

Goldy

[Mikemv]

Goldy, thanks for posting about airspeed. That was what I was getting at in asking about a "Cruise" definition.

 

Now, I have a problem with the 2 stated processes. HG says 4-5 inches below MAP at cruise. Is cruise in R22 faster than 60kts? I think it would be. Goldy states slow to 60kts and then have 3-4 inches reserve below MAP. 60kts should require less MP than "Cruise" so why then have less reserve under MAP?

 

Please do not misunderstand me. I am not saying either process is wrong or invalid, just questioning the reserve numbers for MP in each process.

 

Also, why "Downwind"? In Cruise flight (75kts?) or at 60kts when S&L, wind direction will not change required MP? If we are flying inbound to an LZ at S&L could we not note MP and make the reserve power available computation to MAP? Maybe verify reserve power during our circling recon? Also, we should be continuing the evaluation process during the approach as we slow (but above ETL) and verify reserve power for termination, planning termination at a low hover or (low recon in progress) to the ground if suitable? Piston or turbine, stated procedure has worked for me.

 

Consider this, if making a high recon at 45kts, more power is required than at 60kts. How much reserve MP do you have from this Airspeed? From 30kts? You will pass thru those airspeeds during the approach but can safely check reserve power at altitude at these speeds?

 

Again, not saying anyones' stated procedure was incorrect. Throwing some proven thought processes out for consideration/use by others. Fly safe, learn from the No hairs and Grey hairs, MikeMV

[lelebebbel]

the idea with this powercheck is the Airspeed vs. Power required curve.

 

The shape of this curve will always be the same (or close to that) for any given aircraft.

In a hover, it will always need a certain amount of power over what it requires to maintain level flight at, for example 60 knots. The power that you need to fly 60 will change depending on weight, temperature etc, but the power to hover will always be a given amount higher than that.

 

After "measuring" what the manifold pressure at 60kts is, you can estimate how much more MAP you would need to hover, and calculate if this would be within the limits (POH or physical) for the aircraft.

 

The numbers I was taught are as follows:

53kts airspeed, S+L, carb heat off, read MAP.

6" margin or higher between whatever you are reading and the limitation should be enough to hover OGE

5" hover IGE

4" zero speed landing without hover....

 

 

Sounds good in theory.

Now, here is the problem with this kind of powercheck for the R22:

 

IT DOES NOT WORK.

 

Try it, it will almost always tell you that you can hover OGE, at least it did for me in any of the R22s that I've flown. No matter if I really was already at the max continuous limit while hovering IGE 5 minutes earlier.

 

If you really want to know if you have enough power to go into a confined area, do a OGE hover check close to the landing site.

Make sure you have a way to dive out of it if it doesn't work. Consider that it might be warmer at the landing site than where you are hovering and add a little safety margin for that.

Edited October 17, 2009 by lelebebbel

[TimW68]

I would have to agree with the last post, if you are really concerned about not having enough power, climb to 1000 ft AGL, 0 airspeed CH off, and take a look at what ya got. This way (1000 ft. AGL) you can set up a safe landing site in the event of a power failure, I would also keep a very close eye on my VSI & ALT. (carb heat off at your discretion)

[kodoz]

All these methods sound...interesting, made-up, and subject to interpretation. If you pass over your LZ and use the temp, elevation, and an estimate of your weight, you can consult you HOGE chart (on your kneeboard). If it's close, risk assessment should be your next step...not "Let's go take a look."

 

Also kinda interesting to see this same thread play out again the same as it has in the past.

[Chewie]

[edit]I knew this topic had been covered before, but it's just so far back in the archives that it's hard to find. Here are some links back if you're interested in seeing them [link], [link], [link], (gets good around the 18th post). If only there was a way to capture all this great info rather than rehashing it anew each time....

 

Ahhh thanks Kodoz, I had searched and couldn't find anything. Figured it had been covered in the past but pruned. I'll check them out!

[kodoz]

Ahhh thanks Kodoz, I had searched and couldn't find anything. Figured it had been covered in the past but pruned. I'll check them out!

 

 

Yes, I was surprised to find 3-year old archived posts. Joker et al provided some excellent info back then. By next week sometime, I'll add it to wikiRFM.

[lelebebbel]

problem with the OGE charts in the R22 is that they also often don't really work. They usually promise you that you can hover OGE when really you can't. At least if your machine isn't brand new...

One of the reasons for that could be that they don't consider relative humidity (as far as I know the numbers are based on 0% RH).

[Goldy]

Goldy, thanks for posting about airspeed. That was what I was getting at in asking about a "Cruise" definition.

 

Now, I have a problem with the 2 stated processes. HG says 4-5 inches below MAP at cruise. Is cruise in R22 faster than 60kts? I think it would be. Goldy states slow to 60kts and then have 3-4 inches reserve below MAP. 60kts should require less MP than "Cruise" so why then have less reserve under MAP?

 

Mike- It's been discussed before, as previous posts mention there is a lot of controversy and "estimating" when using these methods. Personally, I don't like using any of them. I never like to tell students to just "put it in a hover, and see how much power you need". Problem with that is, the ship is more unstable in a hover (with a young pilot, wind, lightweight, etc.) and in the event of an actual failure, requires more skill for an auto.

 

I still use the charts, over estimate my DA, round up my weight, etc. to build in a safety margin. Probably similar to the way many guys do it. Then whenever possible on a high DA landing, I make a shallow approach so I always have ETL or ground effect working for me. You can go from 3 feet to the ground pretty easy if you run out of power and have to do a run on. Try doing that from a steep approach!

 

Right as you start to terminate your landing into a hover is where you know you will need the most power, so I am always quick on the throttle in case RPM starts to droop. I guess I am hijacking this thread from "Power Checks" to "Landing in high DA" !!

 

Goldy

Edited October 17, 2009 by Goldy

[TimW68]

I never like to tell students to just "put it in a hover, and see how much power you need". Problem with that is, the ship is more unstable in a hover (with a young pilot, wind, lightweight, etc.) and in the event of an actual failure, requires more skill for an auto.

 

Goldy - this was in reference to a confined entry, with a runway and nothing to worry about clearing on the way out there are plenty of options for the check. I understand your point of how things can go wrong in an OGE hover, but I never stated to just haphazardly go into an OGE hover as you implied. At 1000' agl and staring at a safe emergency landing site I would like to know if I'm going to exceed MP limits, or for that matter be able to get out and clear obstructions without telling my pax to look for another ride. Have set up quite a few times for settling w/power demonstrations in this config. and have a small amount of training in 0-speed auto's from altitude. Not saying I am in any hurry to do one, and I know you have allot more time in the seat than I do. At my hour level and for most students really there is no reason to be doing confined entry's except for practice, with a CFI, or my guess is I would have allot of explaining to do to my school as to why I disregarded the renal agreement if anything happened. Most of the comm./higher time pilots do their power checks right at the airport before departure with a max per. take-off or a 20-30 ft hover from what I've seen.

[Hovergirl]

Goldy, thanks for posting about airspeed. That was what I was getting at in asking about a "Cruise" definition.

 

Now, I have a problem with the 2 stated processes. HG says 4-5 inches below MAP at cruise. Is cruise in R22 faster than 60kts? I think it would be. Goldy states slow to 60kts and then have 3-4 inches reserve below MAP. 60kts should require less MP than "Cruise" so why then have less reserve under MAP?

 

Please do not misunderstand me. I am not saying either process is wrong or invalid, just questioning the reserve numbers for MP in each process.

 

Also, why "Downwind"? In Cruise flight (75kts?) or at 60kts when S&L, wind direction will not change required MP? If we are flying inbound to an LZ at S&L could we not note MP and make the reserve power available computation to MAP? Maybe verify reserve power during our circling recon? Also, we should be continuing the evaluation process during the approach as we slow (but above ETL) and verify reserve power for termination, planning termination at a low hover or (low recon in progress) to the ground if suitable? Piston or turbine, stated procedure has worked for me.

 

Thanks Goldy, I did forget airspeed (55 kts is what I learned) -- a 'minor' detail

I think the reference to downwind just came because of the original wording of the question, which referred to a power check on the downwind, not because direction of flight was actually important.

 

I personally do not like relying on charts to tell me what I can do (on a clear day in Torrance with a brand new ship and a 10,000 hr pilot ) but rather use them to tell me what I can't/shouldn't do. As far as possibilities, I like practically checking whether I have power for an OGE hover, and then keeping an eye on how much power I'm using as I fly around doing my recon. I was trained to fly 500 ft agl s&l above the spot (up or downwind was not specified) to see what my power margin was before starting the recon, but I think they changed to an OGE hover power check later.

 

As for whether this sort of check puts you in a dangerous spot, it does so some extent. But it's also risky heading into a confined area if you don't know if you have enough power to land there or stop your descent. I personally prefer the former and like to have as much information as possible before I head into that clearing... (and don't forget to calculate your emergency power for when those wires suddenly appear! But that's a different thread.)

 

Thanks for taking up the thread guys while I stepped away. IMO confined areas and pinnacles are what helicopters are all about, (VFR at least) since they use so many different skills and require actual decision making and risk assessment above and beyond flying the maneuvers and staying in the pattern again, and again...

[JDHelicopterPilot]

This is a great thread and of course covered already but still a good read. It's been so long since I have flown the R-22 and 300CB. Make sure you remember the "power check" is not really done the same way for the R-22 and 300CB. One, if I remember the 300CB doesn't have a limited MP like that of the R-22.

 

Best bet guys and gals is to talk with your CFI. However, I bet there are more than a few CFI's out there who do not know the answer. I actualy have a hand out some where at home on how to do a power check in the R-22. It included recomended power margins for each type of approach. When I get home I will try to track that hand out down. These are only rules of thumb though. You should always consult the RFM performance section.

 

Keep in mind that some areas we land at may not allow for keeping ETL most of the way in until ground effect. Most of my approaches are very steep due to the nature of my flying. ETL is lost very early in the approch often. That unless it is a pretty windy day. My desent rate is often 200'/min sometimes a little lower. As a result the bulk of my power is already pulled in. If ETL is lost before getting below your obstructions and you realize you don't have the power to stop then you will still have some time to get ETL back and go around. In other words, even after a doing a power check and finding you have "enough" power, leave yourself a way out!

 

If you go below your obstructions prior to loosing ETL and then lose ETL and realize you don't have the power you thought, then you could be in a world of hurt. Please keep in mind that each LZ is different. Some are larger and you can land with ETL other are tighter and require a very steep approach. Your approach will then vary as a result. It isn't one size fits all and that is what I taught my students.

 

 

 

I will try to find that handout. If I do I will try to get it on here.

 

JD

Edited October 18, 2009 by JDHelicopterPilot

[RkyMtnHI]

All these methods sound...interesting, made-up, and subject to interpretation. If you pass over your LZ and use the temp, elevation, and an estimate of your weight, you can consult you HOGE chart (on your kneeboard). If it's close, risk assessment should be your next step...not "Let's go take a look."

 

Also kinda interesting to see this same thread play out again the same as it has in the past.

 

 

thought of this many times before... please pm me so we can talk about this idea..

 

this is a great topic.. the reason i come back to VR time and again.

 

dp

[Goldy]

I will try to find that handout. If I do I will try to get it on here.

 

JD

 

JD- I just looked for mine but no luck. I also searched thru the factory R22 Flight Training Guide. Although it has a section devoted to describing various maneuvers, it says nothing about power checks!

 

Maybe its all a myth.

 

Goldy

[JDHelicopterPilot]

Goldy,

 

I don't think it was put out by the factory. Rather it was one made by my CFI or flight school. It was pretty good. I won't be home until WED. so I'll look for it then.

 

JD

[Chewie]

I came across this just now, though the example is for a Robbie,

CAA Helicopter Safety booklet.

 

From page 22-23...

 

"Prior to Landing

Many landings are preceded by a hover, and since power required to hover is greater than that required for forward flight, it follows that special care is needed for landings at high gross weights in high density altitudes. Keeping the wind on the nose is essential in such circumstances. The method for assessing the power in hand before landing is based on similar principles to that used for the takeoff, except that it is normally done in forward flight and at an altitude slightly above the landing site. It is usually accomplished as follows:

 

• Fly straight and level at a pre-determined

speed (usually minimum-power speed)

with landing rotor rpm selected, taking

care to avoid air that is subject to up or

downdraughts.

 

• Note the manifold pressure or torque.

 

• While maintaining the same rotor rpm,

briefly apply full power and note the

corresponding change in manifold

pressure or torque. (Note that it is usually

not practical or necessary to maintain

the same airspeed at this point.)

 

• The difference between the two values

gives a clear indication of the type of

approach and landing that can be safely

carried out at the site.

 

Any headwind component will obviously be an advantage here, but it should not be relied upon, as it may abate just when you need it most.

 

Using the R22 as an example, six inches of excess MAP should enable an approach to be made to an OGE hover, whereas just three inches of excess MAP will usually mean that only a run-on

landing will be possible – but this is not recommended. Refer to the Flight Manual for specifics.

 

An alternative method is to check the power required to hover OGE adjacent to the landing site, and compare it with the power available. It is essential that this is done with pre-determined escape route in mind over a clear area with plenty of height to spare, as the amount of power required to hover OGE at high density altitudes is extremely large. The helicopter can quickly develop a high rate of descent if there is insufficient power available. Beware of vortex ring state"

[lelebebbel]

Using the R22 as an example, six inches of excess MAP should enable an approach to be made to an OGE hover, whereas just three inches of excess MAP will usually mean that only a run-on

landing will be possible – but this is not recommended. Refer to the Flight Manual for specifics.

 

 

like i said earlier - sounds nice, but it does not work in real life. You can get that "6 inch" reserve in almost any R22 at 53kts, fully loaded, even if it barely hovers IGE and here is no way you could hover OGE without busting the MAP limit.

 

I have heard this 6-inch myth from many sources including the school i worked at, but I have no idea where it came from. If this was actually number that somebody measured, then there should also be a different value for Beta 2s vs Betas, but there isn't.

 

The method is not in the flight manual.

[Chewie]

The method is not in the flight manual.

 

That was going to be my other question lol.