Hovering question
Globo, no the same phycics apply and they hover left wheel low.
Only aircraft that addressed the issue to my knowledge are the Sikorsky S-64 Skycrane and the Kaman UH-2 ( recall being told that anyway ), and the solution there was to design in ( 3 degrees in the case of the 64 ) lateral main rotor shaft tilt.
Only aircraft that addressed the issue to my knowledge are the Sikorsky S-64 Skycrane and the Kaman UH-2 ( recall being told that anyway ), and the solution there was to design in ( 3 degrees in the case of the 64 ) lateral main rotor shaft tilt.
Back to the OP. It is one of the joys of rotary wing flying ( there are many ) which no one gets unless you’ve tried it.
It is one of the joys of rotary wing flying ( there are many )
Thread Starter
Thanks for the very informative replies, this characteristic does seem more pronounced on some types than others
One poster indicated this can be ‘engineered out’ to some extent ?
I would think that would be desirable and something all helicopter manufacturers would strive for ?
One other thing, does this slight angle of bank while hovering require a small cyclic input or is it ‘built in’ with a centered cyclic maintaining the bank ?
One poster indicated this can be ‘engineered out’ to some extent ?
I would think that would be desirable and something all helicopter manufacturers would strive for ?
One other thing, does this slight angle of bank while hovering require a small cyclic input or is it ‘built in’ with a centered cyclic maintaining the bank ?
Thanks for the very informative replies, this characteristic does seem more pronounced on some types than others
One poster indicated this can be ‘engineered out’ to some extent ?
I would think that would be desirable and something all helicopter manufacturers would strive for ?
One other thing, does this slight angle of bank while hovering require a small cyclic input or is it ‘built in’ with a centered cyclic maintaining the bank ?
One poster indicated this can be ‘engineered out’ to some extent ?
I would think that would be desirable and something all helicopter manufacturers would strive for ?
One other thing, does this slight angle of bank while hovering require a small cyclic input or is it ‘built in’ with a centered cyclic maintaining the bank ?
One other thing, does this slight angle of bank while hovering require a small cyclic input or is it ‘built in’ with a centered cyclic maintaining the bank ?
In some respects there is no merit in engineering this out, as this leads to mechanical overcomplication of what is an already complicated device. And of course added cost.
As stated, aside from the aerodynamic interactions of the tail rotor and main rotor(s) the BMI and indeed distribution of your punters/ stores/ arrays and indeed ordinance can affect all this. The Gazelle could on occasion hover one skid low but also with an aft inclination of the skid. Which required a gentle touch; in fact the thing is still technically in the hover until she’s finally on the deck, which can be witnessed on occasion by ab initiates (and it has to be said even experienced old f@rts) ‘cyclic hopping’ around the tarmac. Aircraft that were designed to deck land on small ships for example tend to have highly absorbent gear to cater for the fact that you couldn’t really demonstrate too much finesse in the final foot or so of landing due to deck pitch and roll, and just had to put it down, irrespective of whether you had one skid or wheel lower than the other.
Once you’ve mastered hovering it becomes second nature, which as another poster has alluded to doesn’t involve too much in the way of grey matter, and which is why in a subjective way is very hard to explain. You just have to observe it and get on with it. All great fun, as is downwind work and transitions, and I for one still miss it.
As stated, aside from the aerodynamic interactions of the tail rotor and main rotor(s) the BMI and indeed distribution of your punters/ stores/ arrays and indeed ordinance can affect all this. The Gazelle could on occasion hover one skid low but also with an aft inclination of the skid. Which required a gentle touch; in fact the thing is still technically in the hover until she’s finally on the deck, which can be witnessed on occasion by ab initiates (and it has to be said even experienced old f@rts) ‘cyclic hopping’ around the tarmac. Aircraft that were designed to deck land on small ships for example tend to have highly absorbent gear to cater for the fact that you couldn’t really demonstrate too much finesse in the final foot or so of landing due to deck pitch and roll, and just had to put it down, irrespective of whether you had one skid or wheel lower than the other.
Once you’ve mastered hovering it becomes second nature, which as another poster has alluded to doesn’t involve too much in the way of grey matter, and which is why in a subjective way is very hard to explain. You just have to observe it and get on with it. All great fun, as is downwind work and transitions, and I for one still miss it.
it’s the same principle as described for tail rotor aircraft. The heads are a foot or two displaced vertically when hovering and thus generate a couple. Because the aft head is doing more of the lifting (ie the c of g is closer to the aft head than the front) the difference in force means that lateral cyclic (and pedals) are needed to maintain the hover.
I assumed that the Kaman Husky would be an exception, not having a tail rotor. A one hour 'famil' wet winching offered no confirmation - the various bits of the airframe were in constant, and contradictory, motion !
Back in the pre-DHFS days at Shawbury, it was always entertaining to see the students transfer from the Gazelle (right skid low) to the Wessex (left wheel low) as in their first take off, they inevitably adopted the Gazelle hover attitude and set off to the right fairly sharply!
All the instructors knew this would happen and were prepared to intervene when required but it was a good teaching point and gave most onlookers a giggle.
For the first hover checks on SAR, the hover attitude was noted as it varied with AUM, C of G and wind conditions and, if conditions outside worsened, the AI could be used - very useful especially over the water.
All the instructors knew this would happen and were prepared to intervene when required but it was a good teaching point and gave most onlookers a giggle.
For the first hover checks on SAR, the hover attitude was noted as it varied with AUM, C of G and wind conditions and, if conditions outside worsened, the AI could be used - very useful especially over the water.
And when the trusty old Gnome’s on the Wessex were slow to start on a cold day, you could always stamp your feet get them going. !
What a great bit of kit that was. One of the few airframes we took off the Yanks and made better.
What a great bit of kit that was. One of the few airframes we took off the Yanks and made better.
Globo, not just the airframe-the Gnomes were GE T-58’s built under license too, as I recall being told.
Last edited by JohnDixson; 3rd Oct 2020 at 13:02. Reason: add’l thought
Yes believe you’re right. In much the same
way as the mighty Bristol Nimbus was developed, I think, from Turbomeca and the Artouste ?
I’ll stand corrected however I think the only home grown engine for helos of that period was probably the Napier Gazelle ? Wx III
way as the mighty Bristol Nimbus was developed, I think, from Turbomeca and the Artouste ?
I’ll stand corrected however I think the only home grown engine for helos of that period was probably the Napier Gazelle ? Wx III
Globo, you wrote: “In some respects there is no merit in engineering this out, as this leads to mechanical overcomplication of what is an already complicated device. “
Amen. Fly the Crane from say 15 to 60 KIAS trim it out and see where the nose is pointing. Suffice to say, SA never repeated the lateral shaft tilt idea.
Also, re my somewhat snarky comment re the Gnomes, here is some reality: when I joined SA in 1966, I was shortly joined in a small cubical by a former USMC pilot back from flying S-58’s in Vietnam. He told me that they were changing engines at 300 hours and did not fly single ship missions with the aircraft due to the engine situation. Strong case for the Gnome addition.
Amen. Fly the Crane from say 15 to 60 KIAS trim it out and see where the nose is pointing. Suffice to say, SA never repeated the lateral shaft tilt idea.
Also, re my somewhat snarky comment re the Gnomes, here is some reality: when I joined SA in 1966, I was shortly joined in a small cubical by a former USMC pilot back from flying S-58’s in Vietnam. He told me that they were changing engines at 300 hours and did not fly single ship missions with the aircraft due to the engine situation. Strong case for the Gnome addition.
So was the RR Gnome the same as a GE T-58, just built better or was the design changed by RR? Did the GE have the fuel computer like the Gnome?
Wikepedia answered my question - yes, same engine - no, fuel computer was De Havilland/Lucas so introduced on the Gnome
Crab, sorry for the thread drift: The first GE electronic supervisory control for the T-58 came to the USN with the T-58-10, around 1966-67, and was called , ( appropriately according to more than a few USN SH-3D pilots ) the PMS. Its in-flight reliability was poor enough to merit SA having to install a PMS cut-off button on the 3D cyclic grips. Thus, when GE announced that the T-700 engine ( for UTTAS -UH-60/61) would arrive with a hybrid hydromechanical and electronic engine control we and I think Boeing were expecting trouble. Turned out that GE had done their homework well and the reliability of the electronic control surpassed that of the hydromechanical unit, and neither were an issue.
Last edited by JohnDixson; 3rd Oct 2020 at 17:40. Reason: spelling