Control & Guidance : A primer

The major lift producing component of an aerospace vehicle is the wing surface and the control deflection is provided by the control surfaces.
When the control moment and the aerodynamic moment are balanced, this state is called the trim state of the vehicle.
For a statically stable vehicle(C.G. ahead of C.P.), the control moment generated by the actuator deflection produces the required AoA, and the moment produced is stabilizing the vehicle.

The case is different for a statically unstable vehicle (C.G. behind C.P.), where this creates a destabilizing moment.

The flying vehicle with a stable configuration can be designed without an autopilot theoretically. However, for precise control of lateral acceleration, autopilot is an integral element in the design procedure.
A trim-state is achieved when the aerodynamic moment generated due to AoA is balanced by the control moment generated due to fin deflection, i.e,

Aerodynamic Moment = Control Moment

Requirement of a trim state

 

 

 

The vehicle’s static stability is directly proportional to the distance between the C.G. and C.P., more the distance, the more is the control effort required to trim the vehicle.

For a high manoeuvring vehicle and where control effort needs to be optimized, it is desired to keep this distance as minimum as possible.

SR-71 Configuration

‘In the Land of White Orchids’- A Day Trip across Kurseong & Darjeeling..Part I

I had only a day to explore Kurseong and with some late planning further in the day….to Darjeeling. Well, this time work has taken me again to this beautiful part of North Bengal. I was staying in Sevoke road near Dooars where people usually go there for vacation and mostly to escape th summer heat. … Continue reading “‘In the Land of White Orchids’- A Day Trip across Kurseong & Darjeeling..Part I”

I had only a day to explore Kurseong and with some late planning further in the day….to Darjeeling.

Well, this time work has taken me again to this beautiful part of North Bengal. I was staying in Sevoke road near Dooars where people usually go there for vacation and mostly to escape th summer heat. This is the same road which takes you to Gangtok and Kalimpong. Little less than 1 hour in flight to Bagdogra..Dooars is a sight to behold with its beautiful clean roads, tea gardens and with the simplicity of the people from the hills..it’s enchanting in some way and you are sure to give your system a refresh.

Morning in Dooars
Sometimes..This is all you need.

I came to know after a hectic Saturday that there is no work on the Sunday and I started planning how to make best use of the Sunday.  From Siliguri, Kurseong is not far. Initially I thought would go to Mirik, later changed my plan to Kurseong. Though 2-3 days in those areas is ideal, still getting a day off is just perfect for my plans.

Sunday morning I woke up around 0630 am in the beautiful Guest House overseeing the morning sunrise. Got served morning coffee and I googled for places to see in Kurseong. I still had to travel to the famed Darjeeling More from the place I was in Dooars.

25 March 2018 Sunday 0700 am:  Woke up 30 mins ago and checking on what are the places to visit in Kurseong. Want to go for a Day Trip to Kurseong today. It takes about 1 hour to reach there and the distance is about 37 km. Lets see if I can start early so that can cover as many places there. Been googling , still in bed and shortlisting the following:

  1. Eagle’s Craig
  2. Makaibari and Goodricke Tea Estates
  3. Monasteries in Sonada and Ghoom
  4. White Orchids
  5. Dow Hill Boarding School
  6. Forest Museum
  7. Netaji Museum
  8. Giddapahar View Point
  9. Victoria School
  10. Railway Museum
  11. Cochrane Place for Lunch

0846 am: Started ..the vehicle came to drop me at Darjeeling More. From here, I will be on my own.  So it’s like this, Sevoke > Checkpost > Darjeeling More.

0925 am: Got a Sumo again…just like 2 years back.These vehicles are prevalent in this road for daily commuters and I just like being in these where we can feel the lifestyle of the locals and have a feeling of their daily lives. In the back seat..and there is this beautiful local girl opposite to me, who is probably visiting her home in Kurseong and two more old men. Had a little chat with them about their whereabouts . It should take about an hour to reach Kurseong. There is a beautiful nepali song the driver is playing in the car, ‘Maya ..terei rahu..saase chalna..’ and recorded the song in my mobile. The trum line is going parallelly with it’s typical sound and the trip is already mesmerizing. There is Mahananda Sanctuary on the way through the Military area. Going through a woody area now ..The roads are just too beautiful..

Reached Kurseong and could feel the temperature drop immediately. With the mountains and hills and a bustling Kurseong Junction..the hills has its own pulse.

Way to Kurseong..
At Kurseong…
You seem to be back in time…
Colors of Life…
He did oblige me for a shot…
Monastery in Kurseong

 

The Dharma Chakra..

 

The Breakfast Place..On road to Dow Hills

1025 am : Walked around the market..visited the Monastery and spent some time with prayers in heart for the close ones. Asked the locals for directions, and Dow Hills is the place they said I should visit. Walked up the road leading to Dow Hills. Been starving, had breakfast in a small resto by the side…they didn’t have much to serve..had roti n sabzi with omlette. After that, walked up some more, got myself a shared maruti van to Dow Hills.It’s interesting to hop onto these vehicvles which we dont find anymore in our cities..

More of Dow Hills experience in the next…

Indigo ground crew at Bagdogra airport saved my day!!

So I was travelling from Bagdogra to Kolkata (IXB-CCU) on 26 March 1635 hrs flight, after my work finished in Siliguri. I got dropped at Bagdogra Airport by about 1500 hours. The mobile network of Jio was not working, so I went up to the counter to show my PNR and asked for the ticket … Continue reading “Indigo ground crew at Bagdogra airport saved my day!!”

So I was travelling from Bagdogra to Kolkata (IXB-CCU) on 26 March 1635 hrs flight, after my work finished in Siliguri. I got dropped at Bagdogra Airport by about 1500 hours. The mobile network of Jio was not working, so I went up to the counter to show my PNR and asked for the ticket printout. To my utter surprise I was told that , the ticket has been cancelled as the payment was declined while booking.I have booked my ticket on 22nd March through mobile app, a day before my onward travel. I have got an email from Indigo mentioning the PNR and the seat no. I didn’t even bother to check if the payment is through or not.

Now , at the counter, I got perturbed as I planned to stay a day in Kolkata in my short trip in the home state and go to Hyderabad a day after. There weren’t much options to take another flight from Bagdogra to Kolkata. I was also told that the flight is running full and there are no available seats in the flight 6E-534. I had to wait for any no-shows. I called up the Customer Care and they told me the same that due to payment link failure, the status of the ticket was in pending and later cancelled. Neither Indigo or the bank have informed this via email/sms.

I went inside and was waiting at the Indigo counter. There was still about 45 mins for the counter closing time. In the mean time, I went up to the Air Asia counter so ask for any availability for Kolkata flight that evening. He checked on his system and first told its not available, later rechecked and told there is only 1 seat available and the flight departs at about 1810 hours.

Came back to Indigo counter to ask the status of ticket availability. They told there are 8 no-shows that time, about 40 mins to go for counter closing. I met this Indigo guy, who was very reassuring and extended all his support. Also, the girl at the ticketing, kept on updating me on the status as I kept on asking them every 5 mins.

I met Indigo Duty Manager that time, Ms. Vijayeta. She was very proactive and told me they can accomodate me if there are any no-shows. At the end, there were 2-3 no-shows I believe at the counter closing time of 45 mins prior to departure which came as good news to me. I gave my details before hand, my details along with card information and at 44 mins before the departure, the boarding pass was in my hand, with a new fresh booking made, though it costed me way more than usual. Ms. Vijayeta took care of the luggage and her staff guided me all the way to the boarding gate of 6E-534 and I thanked her for the support from her end. Though I was gutted but on the positive side was impressed with the entire Indigo ground team who extended all the support that was required. I boarded the flight and landed in Kolkata as per schedule and met family and friends in my planned short stay at home in Kolkata.

This episode taught me a lesson to check the ticket carefully from next time which comes in the mail and also to look at the status of the ticket. Also, wish the airlines send me an email/sms saying about the declined payment so that I wouldn’t have gone through this episode at all, leaving aside a new fresh booking for higher ticket price.

However, this is how my stay in Bagdogra concluded on what was otherwise a beautiful trip around Dooars, Kurseong and Darjeeling. More of that later…

About Cruciform Missile : Difference between + and x flying orientation

MISSILES, historically, and even in current design and development are of cruciform type with low aspect ratio wing/control fins. This was mainly due to carriage point of view and more often than not, it needs to be stored in launch tube/canister unlike aircraft with high aspect ratio surfaces. In most instances, missiles fly in “plus … Continue reading “About Cruciform Missile : Difference between + and x flying orientation”

MISSILES, historically, and even in current design and development are of cruciform type with low aspect ratio wing/control fins. This was mainly due to carriage point of view and more often than not, it needs to be stored in launch tube/canister unlike aircraft with high aspect ratio surfaces. In most instances, missiles fly in “plus +” or “cross x” orientation.

Considering pitch control of a cruciform missile, in “plus” configuration, if both the horizontal fins are deflected downward, by an amount δ, this results in an upward force F in the pitch axis. Now , the same missile with 45° roll orientation and all the four control fin deflected downward by an amount δ, a force equivalent to √2 times of the force F is produced in the vertical plane in the “cross” configuration.

Body axis coordinate system

 

Definition of Wind and Body axes flight parameters