g loading during turns
 

Does anybody know what the maximum G force the Bell 206 JetRanger is rated for during turns or during forward of vertical decelerations?
Is it merely the max gross weight of the aircraft i.e. when fully loaded you cannot exceed 1G during a turn?

If you couldn't exceed 1g, then you couldn't hold altitude in a turn.

Most choppers are able to comfortably hold 2.7g, which is a 60 degree bank level turn, plus a wind gust. The normal envelope starts at 0kts and 1g, stays level at 1g heading to the right to Vne, goes vertical, or a bit backwards to 2.7, then goes level left back to 60kt or a bit less, where the machine can't pull that much, and slopes back down to the starting point of 0kt/1g. Teetering heads are not allowed to fly at less than 1g.

Some rigid heads, like the BK117, are certified to 3.5g, which means the rotor system can cope with a bit more than that. Envelope starts at 0kt/1g but dives down to include -1g and the top limit was 3.5g. Considerably bigger.

It's not normally a problem of the airframe being able to handle the g it is usually having enough power to sustain it - you are doubling the weight of the helicopter in a 60 deg bank turn - 2g - and many can only manage it by reducing speed in the turn as they go.

I was once criticised by a certain flight commander during an IF training trip for allowing my Puma to descend in the 60 degree bank turn that he told to me to maintain. He wasn’t very experienced on type as an IF safety pilot. I pointed out that we were at maximum allowable collective pitch and the aircraft simply couldn’t maintain level flight at that angle of bank so to maintain the airspeed he wanted, it could only descend, bearing in mind that he told me to maintain 120 kts. As a safety pilot myself (and then later a QHI on type) I never expected any pilot to use more than 45 degrees of bank for practicing steep turns.

IIRC a Puma could maintain a 60 degree banked turn at a constant height at 80-90 knots with an AUW of around 7,000 K.

You didn't arf go around fast, like.

point five "g" on the Huey and Kiowa. From Huey manual,

8-53. Low G Maneuvers.
WARNING - Intentional flight below +0.5 G is prohibited.

WARNING - Abrupt inputs of flight controls cause excessive main rotor flapping, which may result in mast bumping and must be avoided.

a. Because of mission requirements, it may be necessary to rapidly lower the nose of the helicopter. At moderate to high airspeeds, It becomes increasingly easier to approach zero or negative load factors by abrupt forward cyclic inputs. The helicopter may exhibit a tendency to roll to the right-simultaneously with the forward cyclic Input.

b. Such things as sideslip, weight and location of external stores and airspeed will affect the seventy of the right roll. Variances In gross weight longitudinal cg, and rotor rpm may affect the roll characteristics The right roll occurs throughout the normal operating airspeed range and becomes more violent at progressively lower load factors. When it is necessary in rapidly lower the nose of the helicopter, it is essential that the pilot monitor changes In roll attitude as the cyclic is moved forward.

c. If the flight envelope is inadvertently exceeded, causing a low "G" condition and right roll, move cyclic aft to return rotor to positive thrust condition, then roll level, continuing flight if mast bumping has not occurred.

I cannot find anything regarding g loading in the JetRanger manual and the multiple pilots and instructors that I spoke with cannot give me a number.
I am wondering that if I do a 45 deg turn at max gross am I exceeding or coming close to some limitation that I am unaware of....probably not but I would like to know what the limits are rather than to just assume.
The POH for my planes give numbers for both plus and negative g's.

If g-loading was an important metric there would be a g-ometer in the panel to shout at you.
You're going to be hitting some other limit before you release your inner Maverick.

Yes, it will probably be the torque or an engine limit. On some it might be the onset of blade stall.

A level 45 degree AoB turn is a 1.4 g manoeuvre - you can generate that by reducing speed during the turn with aft cyclic or by maintaining speed and adding collective (power). Or a combination of the two.

Quite why you would want to explore the g limits of a jetranger is rather beyond me:)

If you know that you cannot pull out of your dive because that would exceed the G limits then you wont die all tensed up.

If you pull too much G in the dive, you wont be able to drop your flying suit and rectally mount the cyclic just prior to impact, or was that just our plan for the BoI?

The earliest FAR 27 I can find is dated 2nd Oct 1964 which is a little over one year prior to the 206 flying and would have applied to the design I assume.

Sec. 27.337

Limit maneuvering load factor.
The rotorcraft must be designed for--
(a) A positive limit maneuvering load factor of 3.5 and a negative limit maneuvering load factor of 1.0; or
(b) Any lesser positive limit maneuvering load factor not less than 2.0, and lesser negative limit maneuvering load factor not less than 0.5, whose probability of being exceeded is shown by analysis and flight test to be extremely remote.

Reading the above FAR can be a bit confusing so the latest ammendment (1990) is included.

§27.337 Limit maneuvering load factor.The rotorcraft must be designed for—

(a) A limit maneuvering load factor ranging from a positive limit of 3.5 to a negative limit of −1.0; or

(b) Any positive limit maneuvering load factor not less than 2.0 and any negative limit maneuvering load factor of not less than −0.5 for which—

(1) The probability of being exceeded is shown by analysis and flight tests to be extremely remote; and

(2) The selected values are appropriate to each weight condition between the design maximum and design minimum weights.

So worse case is para (b), your limits would be at least +2 and not less than +0.5 for a 206.

From the graph you can see 2 g comes from a balanced turn at 60° of bank, 3.5 g at 73°, of course you may not have the power available to maintain altitude so decent will be necessary.

The 206B-1 manual states a in the Limitations section "Flight at less than 0.5 g is prohibited", so you can take it as read that it would apply to all 206's. The 206B-1 history - Military (Kiowa), Bell serial numbers 44501 to 44556, first twelve built in the USA, the rest in Australia, unique version to Australia as far as I can gather, just a regular 206 really with ability to fit two stretchers, winch, different cargo hook system to regular 206, plumbed to take an overload fuel tank that could be fitted on rear seat, and of course military avionics.


https://cimg9.ibsrv.net/gimg/pprune....0de01adf65.gif

I have flown up to 3 g in a Lynx with a g meter and it is quite uncomfortable compared to 4 or 5 g in a FW (purely psychological I'm sure) - definitely wouldn't want to go there in a 206!

As well as mast bumping, teetering heads exhibit pronounced anti-flare effects when "bunting".

As in Nr decay?

That would be troublesome, because the g in non-accelerated flight (ie. straight and level, steady climb, steady descent) must average exactly1g. Given there will inevitably be times when it is slightly above 1g, also by definition, there must be times when it is similarly below 1g.

How would a helicopter ever level off from a climb or enter a descent if what you claim were true?

Where is it said that teetering heads are not allowed to fly at less than 1g?

Should be in the RFM/Operators Manual. All of the teetering systems I have flown have had a +.5g limitation.

Do you honestly believe that you could accidentally exceed a design/certification limit simply by performing a banked turn?

We agree, so I'm not sure what your point is? The +0.5g limitation is totally different from Ascend Charlie stating they "are not allowed to fly at less than 1g", which is why I was asking AC where they'd ever seen that.

I certainly don't know of any RFM / Operators Manual that states you're not allowed to fly at less than 1g, because that would mean you couldn't fly it at all!... which was exactly my point.