LSA collapses nose gear on hard landing

Here is a YouTube video from 2009 that I came across today: [click here]

There is a camera mounted in the cockpit that is forward looking and captures the landing. It’s hard to conclude exactly what all the causes of the accident were from the video but it does give a very good view of the accident.

In the video, the student (who uploaded this video), believes that the aircraft stalled before impacting the runway the first time. Based on the airspeed indicator, the behaviour of the aircraft before hitting the runway and bounce afterwards, it seems pretty clear that the aircraft didn’t stall. The airspeed right before the aircraft pitched down, a split second before impact, appeared to be about 53mph and the stall speed (based on the airspeed indicator and flaps up) appears to be 49mph. Pictures after the accident show that the flaps were retracted, and being up would give the highest stall speed. Also, the aircraft was below gross weight and the CG was aft of the forward limit, both factors contributing to a slower stall speed than 49mph. There was no buffet or sudden drop of the nose; the nose appeared to smoothly drop slightly before impact. The aircraft appeared to be able to “fly” after the bounce, something that wouldn’t happen if the airplane was actually stalled.

The only information I have about this accident is what is included in the video. Based on the video and my experience, this is how I think it happened. As the aircraft was brought into the flare it would be slowing down continuously until touchdown, hence, requiring the pilot to pull back further and further on the stick to compensate for the loss of speed. It seems like the pilot initially flared and pulled back a little more to keep the aircraft level, but after a short time, he released the back pressure and the nose dropped, hitting the runway for the first time. I’ve seen this happen a number of times where the student releases back pressure typically because they’re anxious to get the aircraft onto the runway, they’re not focusing on the flare or they’re focusing at a point which is not giving satisfactory peripheral information on their descent. I always tell my students to never lower the nose after you’ve started the flare. There are cases where lowering the nose would be the correct thing to do but it’s a rare situation and it’s usually when you’ve gotten the nose too high that full power wouldn’t be able to prevent a stall; I would say it’s inexcusable to get into that situation. When the initial impact happens it’s somewhat startling to the pilot and the force of impact will actually move the stick forward because of the momentum of the elevator, which wants to continue downwards after the aircraft hits the ground. That will happen with any hard landing and is sometimes not recognized by the pilot. The pilot in this case stated in the video that he “didn’t remember a thing” regarding what he did with the stick after impacting the first time. He most likely didn’t move the stick forward consciously, but it was moved forward because of the momentum of the elevator. After hitting the first time the aircraft bounced, but since the stick had been pushed forward, the aircraft was “flown” back onto the runway a split second later. If the elevator hadn’t moved down after the first impact and the pilot held the attitude constant after, it’s likely the aircraft would have touched down on the mains after the bounce even if no power was used to cushion the landing.

The main cause of the accident was when the pilot released the back pressure prior to the initial impact. At that point he had gone lax on the stick and, since he was lax on the stick, the elevator easily moved down after the first impact, causing the second impact to be quite nose down and a very short time afterwards.

A few recommendations:

1. Don’t rush getting the airplane on the ground.
2. If you do bounce, “freeze” the attitude by doing whatever you have to with the yoke/stick, and from there you can either re-flare or add power to control the touchdown. If you have to add power you should typically do it either at the top of the bounce or as you’re coming down, depending on the conditions. If you add it as you’re rising after the bounce, you’ll likely extend your bounce higher.
3. Your eyes should begin transitioning from your aiming point to at least 1000′ down the runway as you start your flare or just before. When you’re looking down at ~1000′, your eyes shouldn’t be focused at that point. If you’re focused on some point down there, your brain won’t be picking up information effectively from your peripheral vision. You should be looking but not focusing, concentrate on your peripheral. You should be getting peripheral information from the area below the point you’re “looking” at and above the nose of the aircraft, and to the left and right of that area.
4. Keep holding back pressure on the yoke/stick after touchdown and release it slowly so that the nose wheel touches the ground gently.
5. Make sure you’re touching down at the proper speed, ideally just above the stall in most cases. If you’re too fast you’ll have a higher chance of landing on the nose wheel first.

Landing is probably one of the most complicated exercises you’ll do in your training and it’s really important that you have a good “feel” for the aircraft while at low speed and to be proficient at landing before your instructor lets you solo. Don’t be upset if you’re struggling with landing the airplane. A lot of the time I find students will have a marked improvement after doing some “armchair flying”. That’s when you sit in a chair in a quiet room with your eyes closed and you go over everything that you did in that landing or circuit or airwork exercise, etc. Review exactly what your instructor told you about the exercise and review your ground notes on the exercise. I promise you that if you put in the time, “armchair flying” after every lesson, you will see results.

Fly safe!

Airplane Performance – Part 1 – Power and Torque

Using basic equations and simple examples this article explains the difference between power and torque and how they affect performance. The equations are meant to illustrate how different variables are affected.

By the end you should know the difference between power and torque and sound edumacated to all your friends!

The concepts here directly apply to automotive engines as well.

Power and Torque

Fly safe!

Stalls – A Case Against Rudder

Here is an article further detailing the stall recovery. It’s a PDF file so I posted it on my Box.net site where you can view it.

It’s not meant to be an exhaustive discussion about stalls so if you have any questions about any of it or want me to answer the questions I asked in the article, just let me know.

Stalls – A Case Against Rudder

Fly safe!

EDIT: I just read this article on Macleans.ca and a quote from it applies to this subject (the link to article is below):

“You need to teach them to get the heck out of that stall. And lowering the nose is the number one rule. Don’t worry about that wing drop, don’t fight that. Just make sure you lower the nose and get the heck out of that dangerous situation.” — Sunjoo Advani, expert in flight simulation, president of a simulation and engineering consulting firm, and spent the past two years coordinating the International Committee for Aviation Training in Extended Envelopes.

Cockpit crisis – Macleans.ca

Power-on Stalls

Concept:

The initial introduction to stalls can make some pilots vow to never intentionally stall an airplane again! Unfortunately, that decision won’t help the pilot develop his/her skills, kinaesthetic sense and intuition (immediate cognition), something that could be of immeasurable help if in a stall situation close to the ground. The kinaesthetic sense and intuition is the “seat of the pants” flying that you will hear about from many experienced pilots. You will eventually get to the point where you can “feel” the aircraft going to stall before it does; when you reach that milestone, you will be more confident in your skills as well as in the aircraft itself.

When a stall happens close to the ground the key is to unstall the wing and then attain maximum performance to regain the altitude lost and avoid impact with obstacles or terrain. Ideally, you will recognize the deterioration of control effectiveness, stall warning, slow speed, etc. before the stall happens and apply proper procedures to return to the region of normal command, ie: speeds greater than maximum endurance speed. During this part of your training you will practice the technique to recover from a power-on stall should you enter one unintentionally.

During some power-on stalls it is possible to have an abrupt and significant wing drop. This is due to yaw/roll being present at the point of stall. As the airplane is slowed down there is decreased airflow over the tail, reducing the effectiveness of the rudder/ailerons and their ability to counteract the yaw/roll being produced by the propeller in the form of asymmetric thrust and torque. For these reasons and more, it’s likely you will have a wing drop while practicing power-on stalls and it will be a significant drop if you happen to forget to use any rudder on entry!

Technique:

• Entry:

1. CALL or HASEL check
2. Set power/flaps
3. Smoothly increase pitch to the stall
4. Coordinate with rudder

• Recovery:

1. Reduce the angle of attack and;
2. Power full
3. Coordinated roll to wings level
4. Smoothly increase pitch to V_Y
5. Flaps up in stages
6. Level off after altitude stabilized

NOTE 1: If you lower the nose to a pitch down attitude before adding the power, don’t add full power, it will cause you to lose more altitude. Wait until the nose is returned to a positive attitude and then apply full power.

NOTE 2: If, for any reason, the airspeed is approaching V_FE then retract the flaps to 0 degrees.

Common Problems:

1. Not keeping your hand on the throttle during entry
2. Not using enough right rudder to counter asymmetric thrust
3. Applying opposite aileron at the point of stall
4. Applying excessive, uncoordinated rudder
5. Forgetting to retract flaps/exceeding flap speed
6. Pitching too abruptly/high on entry

Tips:

1. When using flap: pitch slightly up to lower speed below V_FE, extend flap and use down elevator to counteract the pitch up moment created by extending the flaps, once the speed has bled off increase the attitude smoothly to the point of stall. This will avoid excessively high attitudes at the point of stall, ie: an unrealistic stall.
2. At slow speeds, ie: during recovery, the ailerons produce excessive adverse yaw, which is normally compensated by the high-speed airflow over the airplane during normal cruise. This requires more rudder than usual to keep the airplane coordinated during the roll to wings level.
3. Relating to common problem #4; the most effective way to create lift is to have the airflow strike the wing head on. Therefore, any slipping or skidding manoeuvre (uncoordinated rudder) would not be effective in recovering from the stall. For the most part that is correct. However, depending on the aircraft, type of stall, and pitch/bank attitude at which the recovery was initiated, using uncoordinated rudder to help control nose drop and yaw/roll could be more effective in the overall recovery of the stall resulting in a smaller altitude loss.

End Note:

Performing stall recoveries with minimum altitude loss is an art. Any small change on the entry of the stall will change the outcome. The more you become familiar with each factor that affects the stall and see how the airplane reacts, the more competent you’ll be at recovering from the stall. It will also increase your overall awareness while flying, especially at reduced speeds, ie: on approach.

Fly safe!

Emergency procedures: more than rote learning

This links into my first post, a quote by Chuck Yeager, about having a thorough understanding of the aircraft systems and emergency equipment/procedures for the aircraft that you’re flying.

“I was always afraid of dying. Always. It was my fear that made me learn everything I could about my airplane and my emergency equipment, and kept me flying respectful of my machine and always alert in the cockpit.”

I wouldn’t say that when I fly I’m always afraid of dying, but over the years I’ve come to really value a complete understanding of all things aviation and foster a respect of the aircraft I’m flying. I started flying when I was 15 years old and at that time I don’t think I could say I had a good respect for the aircraft; I was at the invincible stage of life and I didn’t know what really happened when outside the limits. Finding out the limits of operation is important in becoming more comfortable due to a greater kinaesthetic sense with the aircraft as well as hard facts on it’s performance. Disclaimer: finding the limits of operation of a new aircraft should be done with a qualified instructor who is current and knowledgeable on the specific aircraft and regardless of aircraft, it should be completed at a sufficiently high altitude to ensure recovery well above the ground. After intimately knowing how the aircraft handles during all stages of flight, what happens when your electrics start to flicker and dim, while flying at night, and you pick up a somewhat pungent smell of burning electrics with a dash of burning plastic?!

I can’t think of something scarier while flying than the unknown. According to Wikipedia, “panic” is a sudden sensation of fear which is so strong as to dominate or prevent reason and logical thinking. In any situation a lack of reason or logical thinking would decrease your performance and in an emergency situation the consequences are substantially higher than every day life. In a panic situation a person would make decisions that they normally wouldn’t while in a relaxed state. It’s easy to say you would have done something differently while you sit on the ground in an air conditioned room, but being in the airplane when the electrical fire starts is a different story. What can you do to protect yourself from panicking while dealing with an emergency? The simple answer: know absolutely everything about your airplane and it’s systems.

I usually ask my students why an emergency procedure says to do something or why it’s in a particular order. For a simple example, in the C152, why does the forced approach procedure say:

Mixture — IDLE CUT-OFF

Fuel Shutoff Valve — OFF

Ignition Switch — OFF

Wing Flaps — AS REQUIRED

Master Switch — OFF

The ignition switch and master switch are right beside each other, why couldn’t we get them at the same time? Most students know that the flaps in the C152 are electric but some won’t link the two. I find most questions lead to an “Ah!” moment and most times the student won’t forget. They’ll also remember the emergency procedure better since they can link it to a reason.

Another example has to do with understanding the electrical system and is based on an actual incident. In this case, the pilot was flying on a cross-country and was in the cruise phase. After looking around outside at the mountains for awhile he did a quick glance at the instruments to make sure everything was running smoothly. He then noticed the “LOW-VOLTAGE” light was illuminated and promptly carried out the emergency procedure for it. Following the emergency procedure, you will turn off the radios and cycle the master switch which he did. He then saw the low voltage light was not lit but the battery was showing a high rate of charge. He followed the excessive charge emergency procedure and then landed at the nearest airport instead of continuing en-route. All was well but did the pilot actually need to land at the closest airport? He didn’t. When the alternator fails it starts drawing directly from the battery. After running your avionics on the battery awhile, the battery percentage has decreased and will now accept a larger amount of charge. When the alternator was switched on the battery accepted the charge and showed a high charge rate, significantly more than the normal “hair on the positive side”. That is normal and would have decreased slowly to a small positive charge if he left the alternator on. The C152 POH states that you should terminate the flight as soon as practical if you have “full scale deflection” and not a higher than normal charge rate.

These are two simple examples that virtually all pilots can relate too. The bigger the aircraft, typically the more complex the systems and the more complex the situations that can happen. By thoroughly understanding the systems on your aircraft you will significantly decrease the unknown when dealing with emergencies and will experience a lot less panic and hopefully no panic in emergency situations. It’s also easier to remember emergency procedures if you understand WHY it says to do something. Rote learning is not advisable for systems and emergencies!

Fly safe!

Boeing’s technology for runway safety

Boeing has been working on new technology to reduce the number of runway incursions, which happen at some of the busiest airports around the world. The changes that Boeing proposes include new flight deck displays, controls, and alerting systems for the pilots, and a modification of current procedures and training. According to data from the FAA, most runway incursions are only pilot deviations, but 78% of those pilot deviations involve General Aviation aircraft. Maybe GA needs runway safety technology more than the airlines!

FAA Data

Boeing AERO Magazine

What goes on behind closed doors..!

Ever wondered what happens in the cockpit of an airliner?! Watch in HD!

Chuck Yeager

“I was always afraid of dying. Always. It was my fear that made me learn everything I could about my airplane and my emergency equipment, and kept me flying respectful of my machine and always alert in the cockpit.”

- General Chuck Yeager