Bigger balls than mine in this 139
Not really a fan of the modes dumping you when airspeed gets under the logic threshold. A long time ago we brought back the airspeed on a 76 to 20 knots on the bottom of an ILS to see what happened on a ' what if ' experiment. It got a bit wobbly but she carried on going down the runway into decel mode. Quite impressive.
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Perhaps what you are noticing is that, in the hover, the orientation of the helicopter is a bit tail low, nose high. This is totally normal for many helicopters. This way, with the required forward rotor disc tilt in cruise, the ship itself is just about level while in that flight regime. So as the ship is picked up, the cyclic must be moved forward as first the nose lifts off, and then the tail, so as to keep the rotor disc level and the pickup nice and vertical. As the pilot transitions into forward flight, the rotor disc, and the entire helicopter, tilts forward about the pitch axis and off it goes.
The same effects also happen about the roll axis. Depending on the direction of main rotor rotation, this aerodynamics involved will cause either the right or left skid or wheel to come up first, and the pilot must also move the cyclic laterally as the helicopter picks up into the hover, again to keep the main rotor disc level and the pickup vertical. And of course the wind also has it's own effects on this process.
In any case there is no trim involved. The way the controls are hydraulically boosted in most helicopters there are no control forces to speak of and any "trim" is merely the displacement of the pilot's hand by a couple of centimeters or so. Indeed, in the small R44 I fly, my trim position indicator is the location of my right hand where it rests on my leg
Very small helicopters without hydraulically boosted controls may have electric trim or no trim. The R22 has no trim except for the rather crude "cruise trim" bungee, which is either on or off. It can actually be rather fatiguing to fly after a while, especially if the rigging isn't exactly correct. The Cabri G2 has electric trim. Unfortunately in the G2 there is so much friction in the controls that it is hard to feel when trim has alleviated control pressures. The Enstroms, and the MD500 series, have electric trim, but I've never flown any of them. I'm sure there are other examples.
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Please excuse my ignorance but how do you trim a helicopter?
Reason I'm asking is on the fb video it went up into hover first, during the transition the tail dipped slightly only to be instantly corrected.
Just wondering if trim is some function of the cyclic control system.
I could google but would rather hear from the horses mouth
ta.
Reason I'm asking is on the fb video it went up into hover first, during the transition the tail dipped slightly only to be instantly corrected.
Just wondering if trim is some function of the cyclic control system.
I could google but would rather hear from the horses mouth
ta.
Pitch and roll trim actuators are installed in parallel with the cyclic stick below LH forward cockpit floor. Trim actuators have full travel authority on the pitch and roll control lines.
Trim actuators can be overridden by pilot commands via a spring-clutch. Actuators are operated by pilot commands or by the AFCS. They convert the command to a mechanical output.
The video may be foreshortening the perspective. The pilot can see what we see and at least the same ahead of the aircraft, which was clearly enough to execute a CAT A take-off profile. Only seeing it from the lens perspective I would also have considered a helipad profile with a 35ft TDP. But as Sir Korsky said, the attitude change may have been unappreciated by the occupants of the cabin on this flight. And the pilot saw what they saw, flew the profile and was clearly at take off safety speed whilst still visible.
The aircraft is being flown by hand weemonkey. The attitude changes are entirely due to pilot inputs to the cyclic probably until just about when they disappear. At that point the pilot would surely have engaged some upper modes on the AFCS.
The aircraft is being flown by hand weemonkey. The attitude changes are entirely due to pilot inputs to the cyclic probably until just about when they disappear. At that point the pilot would surely have engaged some upper modes on the AFCS.
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Dont get confused between what the FMS can do, and the limitations which the helicopter is certified for in section 1 of the RFM. (PAGE 1-7) The Vmini is 50 KIAS. So no matter what modes you use, you are not certified to use them in IMC below 50. ( Although it is badly worded, and described as minimum speed for flight in IFR - clearly you can fly IFR in VMC. The key point is, you need to be >50 kts if you are in cloud. That is why, for example you would do a clear area profile in low visibility, because your VToss also happens to be Vmini - you get to a safe IMC speed before you go into cloud.
Last edited by Non-PC Plod; 10th Feb 2020 at 03:29.
The Vmini is 50 KIAS. So no matter what modes you use, you are not certified to use them in IMC below 50 The key point is, you need to be >50 kts if you are in cloud. That is why, for example you would do a clear area profile in low visibility, because your VToss also happens to be Vmini - you get to a safe IMC speed before you go into cloud.
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Maybe, but if you have a low cloudbase, you are always going to be higher when you get to 50 KIAS using a helipad profile than using a clear area profile, since you are accelerating through 4about 0 KIAS as you pass 30' on the way to VTOSS, instead of having zero airspeed and high ROC at 35'.
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Plod,
with all respect, that is not the whole truth with A139... (Ref post #28) Supplement 69 gives an additional limitation:
SAR LIMITATIONS
Flight below 50 KIAS (Vmini) in IMC is only permitted when coupled to a SAR mode.
with all respect, that is not the whole truth with A139... (Ref post #28) Supplement 69 gives an additional limitation:
SAR LIMITATIONS
Flight below 50 KIAS (Vmini) in IMC is only permitted when coupled to a SAR mode.
Maybe, but if you have a low cloudbase, you are always going to be higher when you get to 50 KIAS using a helipad profile than using a clear area profile, since you are accelerating through 4about 0 KIAS as you pass 30' on the way to VTOSS, instead of having zero airspeed and high ROC at 35'.
Last edited by Torquetalk; 10th Feb 2020 at 19:30.
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Accepted. Clearly a vertical profile would be a daft choice if there was any risk of losing visual references before achieving stabilized flight.
If you have engaged "upper modes" of the Autopilot system....is that "stabilized flight" no matter the ground speed of the aircraft?
I specify ground speed because Wind Speed would be sensed as IAS.
Also to remind some of you young folks.....there was a time that "zero/zero" takeoffs were done in helicopters that had not stabilization systems or autopilots at all.
They were done as a matter of course, day and night, for years.
They were all "towering" type takeoffs that were far more vertical than they were transitions into forward flight then a climb away from the surface.
So all of this arguing back and forth about profiles, airspeeds, and the like are indicative of letting Rules getting in the way of aviating.
We have seen adherence to Take Off profiles at night in a cow pasture kill people.
We might assume leaving a beach on an Island at night might also have come to grief for the same reason.
What is patently plain to this old Git is far too many of you "think" you know your numbers and profiles....but don't.
I will give you this....the CAA and other Authorities have not done you any benefit by conjuring up all of these complicated Profiles and Limitations.
Just as we see Sim Training focus upon the wrong things....again usually caused by those same thoughtless rules and regulations.....we see complexity overtake commonsense rule making.
Are ya'll being taught right or just find yourself being the bulge in the Python's stomach?
SAS, these days its all about having full accountability across the performance spectrum, just like your airliner, the days of IMC take off in the Huey in zero/zero are long past, though I do recall zero/zero conditions departing platforms in twins (with no accountability).
Teaching these to the army cadets sure was a crap shoot. Some of the kids just got it off the bat and others you'd just wonder how they got through the cracks. Fun times.
The IF take off - our version of your zero/zero take off is still taught in the Brit Mil - because it works.
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A couple of points to be considered when reading that statement.
If you have engaged "upper modes" of the Autopilot system....is that "stabilized flight" no matter the ground speed of the aircraft?
I specify ground speed because Wind Speed would be sensed as IAS.
Also to remind some of you young folks.....there was a time that "zero/zero" takeoffs were done in helicopters that had not stabilization systems or autopilots at all.
They were done as a matter of course, day and night, for years.
They were all "towering" type takeoffs that were far more vertical than they were transitions into forward flight then a climb away from the surface.
So all of this arguing back and forth about profiles, airspeeds, and the like are indicative of letting Rules getting in the way of aviating.
We have seen adherence to Take Off profiles at night in a cow pasture kill people.
We might assume leaving a beach on an Island at night might also have come to grief for the same reason.
What is patently plain to this old Git is far too many of you "think" you know your numbers and profiles....but don't.
I will give you this....the CAA and other Authorities have not done you any benefit by conjuring up all of these complicated Profiles and Limitations.
Just as we see Sim Training focus upon the wrong things....again usually caused by those same thoughtless rules and regulations.....we see complexity overtake commonsense rule making.
Are ya'll being taught right or just find yourself being the bulge in the Python's stomach?
If you have engaged "upper modes" of the Autopilot system....is that "stabilized flight" no matter the ground speed of the aircraft?
I specify ground speed because Wind Speed would be sensed as IAS.
Also to remind some of you young folks.....there was a time that "zero/zero" takeoffs were done in helicopters that had not stabilization systems or autopilots at all.
They were done as a matter of course, day and night, for years.
They were all "towering" type takeoffs that were far more vertical than they were transitions into forward flight then a climb away from the surface.
So all of this arguing back and forth about profiles, airspeeds, and the like are indicative of letting Rules getting in the way of aviating.
We have seen adherence to Take Off profiles at night in a cow pasture kill people.
We might assume leaving a beach on an Island at night might also have come to grief for the same reason.
What is patently plain to this old Git is far too many of you "think" you know your numbers and profiles....but don't.
I will give you this....the CAA and other Authorities have not done you any benefit by conjuring up all of these complicated Profiles and Limitations.
Just as we see Sim Training focus upon the wrong things....again usually caused by those same thoughtless rules and regulations.....we see complexity overtake commonsense rule making.
Are ya'll being taught right or just find yourself being the bulge in the Python's stomach?
I think there are 2 important points here:
1. Of course the automation can take you away nicely if you ask it to. And us old farts were trained to do imc zero zero departures. But- cash rules, and aircraft are not certified (or insured I guess) for flight IMC below Vmini, because the manufacturer needs to make sure all the redundancy is built- in and nobody is going to sue because of an accident arising from stability issues with a single AP failure at low airspeed.
2. A lot of people seem to have a hangup about Cat A profiles, whilst forgetting where and when they are appropriate. Of course we teach them during initial training, but its down to the pilot to select the appropriate departure when he is out on his own, without forgetting the basics: eg a limitation in the RFM is a limitation, and you cant ignore it; A takeoff over the sea at night is going to be IMC, cos you are going to have no discernable horizon, and very limited surface contact.
So, if you are commercial air transport, you have to follow the rules. If you have more freedom as a private/ corporate etc operator, then you use your own discretion. Unfortunately, this also makes you statistically much more likely to join the list of tragedies! And those are the types of operators in all your examples.
A couple of points to be considered when reading that statement.
If you have engaged "upper modes" of the Autopilot system....is that "stabilized flight" no matter the ground speed of the aircraft?
I specify ground speed because Wind Speed would be sensed as IAS.
Also to remind some of you young folks.....there was a time that "zero/zero" takeoffs were done in helicopters that had not stabilization systems or autopilots at all.
They were done as a matter of course, day and night, for years.
They were all "towering" type takeoffs that were far more vertical than they were transitions into forward flight then a climb away from the surface.
So all of this arguing back and forth about profiles, airspeeds, and the like are indicative of letting Rules getting in the way of aviating.
We have seen adherence to Take Off profiles at night in a cow pasture kill people.
We might assume leaving a beach on an Island at night might also have come to grief for the same reason.
What is patently plain to this old Git is far too many of you "think" you know your numbers and profiles....but don't.
I will give you this....the CAA and other Authorities have not done you any benefit by conjuring up all of these complicated Profiles and Limitations.
Just as we see Sim Training focus upon the wrong things....again usually caused by those same thoughtless rules and regulations.....we see complexity overtake commonsense rule making.
Are ya'll being taught right or just find yourself being the bulge in the Python's stomach?
If you have engaged "upper modes" of the Autopilot system....is that "stabilized flight" no matter the ground speed of the aircraft?
I specify ground speed because Wind Speed would be sensed as IAS.
Also to remind some of you young folks.....there was a time that "zero/zero" takeoffs were done in helicopters that had not stabilization systems or autopilots at all.
They were done as a matter of course, day and night, for years.
They were all "towering" type takeoffs that were far more vertical than they were transitions into forward flight then a climb away from the surface.
So all of this arguing back and forth about profiles, airspeeds, and the like are indicative of letting Rules getting in the way of aviating.
We have seen adherence to Take Off profiles at night in a cow pasture kill people.
We might assume leaving a beach on an Island at night might also have come to grief for the same reason.
What is patently plain to this old Git is far too many of you "think" you know your numbers and profiles....but don't.
I will give you this....the CAA and other Authorities have not done you any benefit by conjuring up all of these complicated Profiles and Limitations.
Just as we see Sim Training focus upon the wrong things....again usually caused by those same thoughtless rules and regulations.....we see complexity overtake commonsense rule making.
Are ya'll being taught right or just find yourself being the bulge in the Python's stomach?
Zero – Zero take-offs are for properly trained mil pilots in a mil environment. They are clearly illegal in pretty much any civilian flight environment. And beyond unacceptable in public transport. The Haughey Air accident a few years ago is a good example of where inadequately trained and practiced crew tried to do something that they should have let be.
My reference to stabilised flight refers to a flight configuration which is safe and, at least short-term, sustainable: Safe attitude, safe airspeed, climbing within performance limits. The aircraft doesn’t care about the groundspeed if it is capable of staying in the air.
I’m sure you will find plenty of support for the idea that excessive regulation and slavish adherence to rules does not make pilots or flying safer. But there is good too. The assumption of authority to take unnecessary risks on the customers’ behalf (with willing or unwilling passengers) is still widespread. I have seen a good number of colleagues fly profiles according to their habits rather than one prescribed by the manufacturer. The increased risk of discounting the possibility to reject clearly flying in the face of common sense.
As to sim training focusing on the wrong thing, that surely depends on your experience. This view doesn’t reflect mine at all. I find there is a good mix in current sim training between hand flying skills, proper use of automation, MCC and startle effects. But the quality of the food depends a lot on the restaurant you choose.
It is not yet known what happened in a certain accident in the Bahamas recently. But I would be very surprised if lack of training or discipline in flying a suitable profile, MCC and currency were not involved.
Unusually, this thread isn’t about a post-CFIT accident due to poor visibility, but a consensus that a safe (and defined) profile was correctly flown.
Avoid imitations
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It should be borne in mind that without a cloud base machine or RVR measuring equipment it is in practice quite difficult in marginal conditions to precisely know the prevailing cloudbase or to accurately estimate the visibility, especially at an off-airport site. Such is the professional helicopter pilot's lot.
However, an ideal (fully safe, fully legal) PT performance departure into IMC can only be flown where the relevant IFR minimum speed to be achieved before visual cues (for a possible reject) are lost. If this isn't achieved and the worst happened, a pilot would have to reject in IMC, at least for the first part of it, in a possibly unstable aircraft - not a clever idea!
It's difficult to see from the video but I'd say that it's most likely that both sets of criteria were met in this case. After all, the static viewpoint of the person holding the camera is not the same as the dynamic viewpoint of the pilot, who would have been able to see even further beyond the the viewpoint of said camera person, as the departure progressed.
However, an ideal (fully safe, fully legal) PT performance departure into IMC can only be flown where the relevant IFR minimum speed to be achieved before visual cues (for a possible reject) are lost. If this isn't achieved and the worst happened, a pilot would have to reject in IMC, at least for the first part of it, in a possibly unstable aircraft - not a clever idea!
It's difficult to see from the video but I'd say that it's most likely that both sets of criteria were met in this case. After all, the static viewpoint of the person holding the camera is not the same as the dynamic viewpoint of the pilot, who would have been able to see even further beyond the the viewpoint of said camera person, as the departure progressed.
